PSYCH 257: Psychopathology

Sources and References

• Barlow, D. H., & Durand, V. M. Abnormal Psychology: An Integrative Approach (8th ed.). Cengage.
• American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders (DSM-5-TR). APA Press, 2022.
• World Health Organization. ICD-11 for Mortality and Morbidity Statistics. WHO, 2022.
• Kring, A. M., Johnson, S. L., Davison, G. C., & Neale, J. M. Abnormal Psychology (14th ed.). Wiley.

Chapter 1: History & Definition of Psychopathology

What Is Abnormal Behaviour?

The 4 Ds framework helps operationalize abnormality:

No single criterion is sufficient; clinicians weigh all four in context. For example, a person who is grieving deeply (distress) but functioning adequately and behaving within cultural norms may not be considered abnormal. Conversely, a person whose behaviour is severely deviant and dangerous but who reports no personal distress (e.g., antisocial personality disorder) would still warrant clinical attention.

Historical Perspectives

Archaeological evidence dates trephination to approximately 6500 BCE. Skulls recovered from Neolithic burial sites across Europe, South America, and Asia show carefully drilled circular holes, many with signs of bone regrowth — indicating that patients survived the procedure. The prevailing interpretation is that ancient healers believed evil spirits occupied the skull and could be released through a physical opening. This represents one of humanity’s earliest surgical interventions and underscores how deeply the supernatural model of mental illness was embedded in early cultures.

The Greek-Roman era introduced naturalistic models. Hippocrates (c. 460–370 BCE) proposed that mental illness stemmed from imbalances among four humours — blood, phlegm, yellow bile, and black bile — anticipating biological psychiatry. Under this system, an excess of black bile produced melancholia (depression), while an excess of yellow bile caused irritability and aggression. Hippocrates also classified mental disturbances into categories including mania, melancholia, and phrenitis (acute mental disturbance with fever), and he advocated for treatments such as rest, diet, and exercise rather than ritual or exorcism. The Roman physician Galen (129–216 CE) extended Hippocratic humorism, linking temperament to humoral balance and establishing a medical tradition that would endure for over a millennium.

The Middle Ages (c. 500–1500 CE) saw a dramatic regression toward demonological explanations across Europe. The mentally ill were increasingly viewed as morally culpable — possessed by demons or in league with the devil. The publication of the Malleus Maleficarum (1486) by Heinrich Kramer and Jacob Sprenger codified procedures for identifying and prosecuting witches, many of whom likely suffered from mental illness. Historians estimate that over 100,000 people were executed during the European witch hunts, a substantial proportion of whom displayed symptoms now recognizable as psychosis, epilepsy, or severe mood disorders. This period represents one of the darkest chapters in the history of mental health treatment.

The Renaissance and Enlightenment brought gradual reforms. Early asylums, such as Bethlem Royal Hospital (“Bedlam”) in London (founded 1247, housed the mentally ill from the 14th century onward), were notorious for squalid conditions and the practice of charging admission to visitors who came to gawk at patients. In Italy, Vincenzo Chiarughi (1759–1820) removed chains from patients at the Hospital of St. Boniface in Florence in 1785 — predating Pinel’s more famous reforms by nearly a decade. Chiarughi advocated for dignified treatment, proper hygiene, and therapeutic engagement, making him one of the earliest champions of humane care.

Philippe Pinel (Paris, 1793) and William Tuke (York Retreat, 1796) championed moral treatment — humane care, fresh air, and structured activity. In North America, Dorothea Dix (1802–1887) was the most influential advocate for institutional reform. After witnessing the horrific conditions in Massachusetts jails where the mentally ill were imprisoned alongside criminals, Dix launched a decades-long campaign that resulted in the establishment of over 30 state psychiatric institutions between 1840 and 1880. Her tireless advocacy extended to Canada and Europe.

In 1908, Clifford Beers published A Mind That Found Itself, a memoir of his own psychiatric hospitalisation that exposed brutal conditions and galvanized the mental hygiene movement. Beers founded the National Committee for Mental Hygiene (now Mental Health America), shifting the conversation toward prevention and public education about mental illness.

The mid-20th century brought deinstitutionalization, driven by the discovery of chlorpromazine (1952), advocacy for civil liberties, and government cost-cutting. While the goal of community-based care was laudable, inadequate funding for outpatient services left many individuals homeless or incarcerated — a phenomenon sometimes called transinstitutionalization.

The 19th–20th centuries brought competing paradigms:

• Biological/medical model (Kraepelin): mental illness as brain disease with distinct categories and prognosis.
• Psychoanalytic model (Freud): unconscious conflict as root cause.
• Behavioural model (Watson, Skinner): learned maladaptive responses.
• Cognitive model (Beck, Ellis): distorted thinking drives disorder.
• Humanistic model (Rogers): blocked self-actualization causes distress.

The Biopsychosocial Model

Modern psychopathology uses a diathesis–stress model: a biological or psychological diathesis (predisposition) interacts with environmental stressors to produce disorder. The broader biopsychosocial model integrates:

• Biological: genetics, neurochemistry, brain structure, epigenetics, immune function
• Psychological: cognitions, emotions, coping styles, personality, developmental history
• Social/cultural: relationships, trauma, socioeconomic status, discrimination, access to resources

These levels are not merely additive — they interact dynamically. A biological vulnerability may only produce disorder in the context of psychological and social risk, and psychological interventions can produce measurable biological changes (e.g., CBT normalises amygdala hyperreactivity in anxiety disorders). This bidirectional influence across levels makes the biopsychosocial model fundamentally integrative rather than reductionist.

The reciprocal gene–environment model extends diathesis–stress by recognising that individuals with certain genetic predispositions may also be more likely to select or create stressful environments (e.g., a person genetically prone to impulsivity may make choices that generate interpersonal conflict), blurring the boundary between genetic and environmental causation.

Cultural Context

Culture-bound syndromes (e.g., ataque de nervios, koro) illustrate that abnormality is partly socially constructed. The DSM-5-TR includes a Cultural Formulation Interview to account for this.

Contemporary Issues: Mental Health Systems

The history of psychopathology continues to evolve. Current challenges include the criminalization of mental illness (in the U.S. and Canada, jails and prisons have become the largest de facto psychiatric institutions), the shortage of mental health professionals in rural and Indigenous communities, the rise of digital mental health interventions (app-based CBT, teletherapy), and the ongoing movement toward recovery-oriented care — a framework that defines success not as the absence of symptoms but as living a meaningful, self-directed life despite ongoing mental health challenges.

Chapter 2: Assessment & Diagnosis

Goals of Clinical Assessment

Assessment Methods

Clinical interviews range from unstructured (open-ended) to fully structured (scripted questions with fixed responses). The Structured Clinical Interview for DSM (SCID) is the gold standard for research diagnostic assessment. The Mini International Neuropsychiatric Interview (MINI) is a shorter structured interview (~15–20 minutes) widely used in clinical settings when time is limited. A semi-structured interview (e.g., the SCID) provides standardized questions but allows the clinician to probe further — balancing reliability with clinical richness. A key advantage of structured formats is improved inter-rater reliability: two clinicians interviewing the same patient are more likely to arrive at the same diagnosis.

The Cultural Formulation Interview (CFI), introduced in DSM-5, is a 16-item set of questions designed to elicit the patient’s cultural identity, cultural conceptualisation of distress, psychosocial stressors, cultural features of vulnerability, and the influence of culture on the clinician–patient relationship. It helps clinicians avoid misdiagnosis driven by cultural unfamiliarity.

Psychological testing includes:

Self-report measures (e.g., Beck Depression Inventory, GAD-7, PHQ-9) provide quantified symptom severity and are cost-effective for screening large populations. Behavioural observation captures naturalistic behaviour; psychophysiological measures (EEG, skin conductance, heart rate variability) index biological reactivity.

Neuroimaging in Assessment

Modern neuroimaging techniques have become valuable in both research and clinical assessment of psychopathology.

While neuroimaging is not yet used for routine diagnosis of most psychiatric disorders, it is increasingly important for differential diagnosis (e.g., distinguishing frontotemporal dementia from depression in older adults) and for research into the neural substrates of disorders.

The DSM System

The DSM-5-TR (2022) — published by the American Psychiatric Association — is the dominant diagnostic system in North America. The ICD-11 (WHO, 2022) is used internationally and is the official coding system for mortality and morbidity statistics in Canada and most countries.

The DSM-5-TR uses a categorical approach: a disorder is present if a minimum number of criteria are met for a specified duration. It abandoned the multiaxial system (Axes I–V) used in DSM-IV but retains dimensional severity ratings for several disorders and has expanded the use of specifiers and cross-cutting dimensional assessments.

Dimensional vs. Categorical Approaches

The categorical approach treats disorders as discrete entities: either a person has major depression or does not. However, research consistently shows that most forms of psychopathology are better described as continuous dimensions — anxiety, depression, and psychosis exist on spectra of severity rather than as all-or-nothing categories.

The Hierarchical Taxonomy of Psychopathology (HiTOP) model organises mental disorders into a hierarchy of dimensional spectra. At the broadest level sits a general p factor (reflecting overall liability to psychopathology), which subdivides into spectra such as internalizing (distress, fear), externalizing (disinhibition, antagonism), and thought disorder (psychosis). These spectra further decompose into subfactors and specific syndromes. HiTOP aims to address the problems of arbitrary diagnostic thresholds, high comorbidity, and within-diagnosis heterogeneity that plague the DSM system. While not yet adopted for clinical use, HiTOP is increasingly influential in research and may shape future editions of diagnostic manuals.

Diagnostic reliability is quantified with Cohen’s kappa (\(\kappa\)):

where \(P_o\) = observed agreement, \(P_e\) = expected agreement by chance. Values \(\kappa > 0.60\) are considered acceptable.

Classification Issues

Several fundamental problems affect psychiatric classification:

Labelling effects: receiving a psychiatric diagnosis can stigmatize and create self-fulfilling prophecies. Rosenhan’s (1973) pseudopatient study demonstrated that once labelled “schizophrenic,” normal behaviours were interpreted through a pathological lens. Modified labelling theory (Link & Phelan) proposes that the mere anticipation of stigma — even before any discrimination occurs — leads individuals with mental illness to withdraw socially, limit their aspirations, and conceal their condition, creating secondary harm beyond the disorder itself.

Cultural bias: diagnostic criteria developed primarily within Western, Educated, Industrialised, Rich, Democratic (WEIRD) populations may pathologize normal minority experiences. For example, hearing voices is considered a hallmark of psychosis in Western psychiatry but is viewed as a spiritual experience in many cultures. Similarly, somatic presentations of depression (common in many Asian and African cultures) may go unrecognised when diagnostic criteria emphasise psychological symptoms.

Overdiagnosis and underdiagnosis: broadened criteria (e.g., ADHD, ASD, bipolar disorder) raise concerns about overdiagnosis and overmedication, particularly in children. Simultaneously, many conditions are underdiagnosed in specific populations — eating disorders in males, ADHD in females, depression in elderly males, and psychotic disorders in racial minority groups who may be misdiagnosed with schizophrenia when presenting with mood symptoms.

Comorbidity: if disorders were truly discrete categories, high rates of co-occurrence would be unexpected. Yet comorbidity is the rule rather than the exception — the majority of individuals with one psychiatric diagnosis meet criteria for at least one other. This may reflect shared underlying dimensions (as the HiTOP model proposes), diagnostic criteria that overlap, or genuine causal relationships between disorders.

Despite limitations, diagnosis serves communication, research, and insurance functions that make it practically indispensable.

Chapter 3: Research Methods in Psychopathology

Why Research Methods Matter

The field of psychopathology depends fundamentally on the quality of its research methods. Claims about etiology (“depression is caused by a chemical imbalance”), prevalence (“1 in 4 people will experience a mental illness”), and treatment efficacy (“this therapy cures anxiety”) can only be evaluated by understanding how the underlying studies were designed. Methodological literacy protects both clinicians and the public from unsubstantiated claims, pseudoscientific treatments, and well-meaning but ineffective interventions.

Research Designs

Case studies provide rich idiographic (individual-level) data but cannot establish causation or generalize to other individuals. They are most useful for rare conditions, generating hypotheses, and illustrating clinical phenomena. Famous case studies in psychopathology include Freud’s “Anna O.” (hysteria), Broca’s patient “Tan” (language localisation), and Sacks’ case studies of neurological patients.

Correlational research measures the statistical association between variables. The Pearson correlation \(r\) ranges from \(-1\) to \(+1\):

Correlation does not imply causation — a third variable (confound) may explain the relationship.

Experimental research randomly assigns participants to conditions, allowing causal inference. The randomized controlled trial (RCT) is the gold standard for treatment efficacy. In a typical RCT, participants are randomly assigned to receive either the experimental treatment or a control condition (waitlist, treatment as usual, or placebo). Random assignment distributes known and unknown confounds approximately equally across groups, so any post-treatment differences can be attributed to the treatment itself. Internal validity (confidence in causal inference) is maximised, though external validity (generalizability to real-world settings) may be limited by strict inclusion criteria and artificial settings.

Meta-analysis statistically combines results across multiple studies to estimate an overall effect size. The effect size (commonly Cohen’s d or the odds ratio) quantifies the magnitude of a treatment effect in standardised units. Meta-analyses sit atop the evidence hierarchy because they synthesise data from numerous studies, increasing statistical power and enabling detection of moderating variables.

Special Designs in Psychopathology

Longitudinal studies track the same individuals over time (prospectively or retrospectively), revealing developmental trajectories and temporal ordering of variables. A prospective longitudinal design follows individuals forward from a risk factor to an outcome (e.g., following children of parents with schizophrenia from birth through adulthood to observe who develops psychosis). These designs are powerful but expensive, time-consuming, and vulnerable to attrition (participants dropping out over time, potentially in non-random ways).

Cross-sectional studies compare different groups (e.g., age groups, diagnostic groups) at one time point — faster and cheaper but confounded by cohort effects (differences between groups may reflect generational experiences rather than developmental change). For example, a cross-sectional study finding lower depression rates in older adults might reflect cohort differences in willingness to report symptoms rather than a genuine decrease in depression with age.

Twin studies partition variance into genetic (heritability, \(h^2\)), shared environmental (experiences common to siblings, e.g., family SES, parenting style), and non-shared environmental components (experiences unique to each sibling, including measurement error). Across psychiatric disorders, non-shared environment consistently accounts for more variance than shared environment, suggesting that even siblings growing up in the same household have substantially different effective environments.

Adoption studies separate genetic from rearing influences by comparing adopted individuals to both biological and adoptive relatives. Molecular genetics (GWAS — Genome-Wide Association Studies) scan millions of genetic variants across thousands of individuals to identify specific risk alleles. For most psychiatric disorders, GWAS have revealed a polygenic architecture — hundreds or thousands of common variants each contributing tiny effects, rather than a few genes of large effect. Polygenic risk scores (PRS) aggregate the effects of these variants into a single number reflecting genetic liability, though current PRS have limited predictive power for individuals.

Analogue, Single-Case, and Epidemiological Designs

Analogue experiments induce mild states (e.g., experimentally induced anxiety via CO₂ inhalation, or sad mood via film clips) in non-clinical samples, allowing experimental control that would be unethical to impose using real pathology. Results must be interpreted cautiously, as analogue states may not fully capture clinical conditions.

Single-case experimental designs (ABAB reversal, multiple baseline) rigorously test interventions in individuals — especially valuable in clinical settings where large samples are impractical.

Epidemiological research measures the distribution of disorders in populations. Two key metrics are:

Prevalence reflects disease burden; incidence reflects disease risk. A condition with high prevalence but low incidence (e.g., chronic schizophrenia) suggests long duration. A condition with rising incidence but stable prevalence (e.g., a rapidly fatal illness) suggests short duration or high mortality. Epidemiological data inform public health policy and resource allocation.

Confounds and Methodological Rigour

A confound (third variable) is any factor that covaries with both the independent and dependent variables, creating a spurious association. Common confounds in psychopathology research include socioeconomic status, comorbid conditions, and medication use. Double-blind procedures — in which neither the participant nor the experimenter knows group assignment — are essential for controlling expectation effects (placebo response, experimenter bias). The placebo effect is particularly powerful in psychiatric treatment trials; antidepressant RCTs typically show 30–40% improvement in placebo groups.

Genetics and Epigenetics in Psychopathology

Quantitative Genetics

Quantitative genetics methods partition the variance in a trait into genetic and environmental components without identifying specific genes. Family studies establish whether a disorder aggregates within families (necessary but not sufficient for genetic causation, as families also share environments). Twin studies compare concordance rates between monozygotic (MZ, ~100% shared DNA) and dizygotic (DZ, ~50% shared DNA) twins; greater MZ than DZ concordance implies genetic influence. Adoption studies separate genetic from environmental transmission by examining whether adopted-away offspring resemble biological or adoptive parents.

Gene–Environment Interaction (G×E)

A gene–environment interaction occurs when the effect of a gene on a disorder depends on the presence of a specific environmental exposure, or vice versa. The classic example is the Caspi et al. (2003) study showing that the short allele of the 5-HTTLPR serotonin transporter gene predicted depression only among individuals who experienced childhood maltreatment. While the specific 5-HTTLPR finding has not consistently replicated, the broader principle of G×E interaction is well established — genes influence sensitivity to environmental risk, and environments influence which genetic vulnerabilities become manifest.

Epigenetics

Epigenetic research has revealed how early environments can have lasting effects on gene expression and behaviour. In landmark animal studies, Michael Meaney and colleagues demonstrated that rat pups receiving high levels of maternal licking and grooming showed increased hippocampal glucocorticoid receptor (GR) expression through reduced DNA methylation of the GR gene promoter. These rats exhibited lower stress reactivity in adulthood. Critically, the effects were transmitted behaviourally: cross-fostered pups adopted the epigenetic profile of their rearing mother, not their biological mother.

Ethics in Research

Participants must provide informed consent, researchers must minimize harm, and data must be kept confidential. Institutional Review Boards (IRBs) or Research Ethics Boards (REBs) in Canada review all human research protocols to ensure ethical standards are met.

The Tuskegee Syphilis Study (1932–1972) remains a landmark cautionary case: the U.S. Public Health Service studied the progression of untreated syphilis in African American men in Alabama without informed consent and even after penicillin became the standard treatment. Participants were actively deceived and denied effective treatment. The study’s exposure in 1972 led to the Belmont Report (1979), which established the foundational principles of modern research ethics — respect for persons (autonomy, informed consent), beneficence (maximize benefit, minimize harm), and justice (equitable distribution of research burdens and benefits). These principles underpin contemporary IRB oversight worldwide.

Chapter 4: Anxiety Disorders

Overview of Anxiety

Anxiety involves three response systems: cognitive (worry, catastrophizing), physiological (autonomic arousal, HPA axis activation), and behavioural (avoidance, escape). Anxiety disorders are the most prevalent class of mental disorders, with a combined lifetime prevalence exceeding 28%.

Separation Anxiety Disorder

Symptoms include persistent worry about losing attachment figures, reluctance to go to school or work, nightmares about separation, and physical complaints (headaches, stomachaches) when separation occurs or is anticipated. Although traditionally considered a childhood disorder, DSM-5 recognises that separation anxiety can persist into or emerge in adulthood. Adult separation anxiety is associated with relationship dependence, difficulty living alone, and comorbid panic disorder and agoraphobia. Prevalence is approximately 4% in children and 1–2% in adults.

Selective Mutism

Selective mutism typically begins before age 5 and is conceptualised as an extreme manifestation of social anxiety in young children. The child is not choosing silence oppositionally; rather, anxiety renders speech nearly impossible in feared contexts. Prevalence is rare (~0.03–1%). Treatment involves graduated exposure to speaking situations and behavioural reinforcement.

Specific Phobia

Intense, irrational fear of a specific object or situation (animals, blood-injection-injury, situational, natural environment, other). Lifetime prevalence ~12%, making it the most common anxiety disorder. Avoidance maintains the phobia via negative reinforcement — each time the person escapes or avoids the feared stimulus, anxiety decreases, reinforcing the avoidance behaviour.

Exposure therapy (systematic desensitization, in vivo flooding) is highly effective, with cure rates exceeding 80% for most specific phobias. Treatment involves constructing an exposure hierarchy — a graded list of feared situations ordered from least to most anxiety-provoking.

The blood-injection-injury (BII) subtype is unique because it involves a biphasic vasovagal response: initial sympathetic arousal (as in other phobias) followed by a sudden parasympathetic surge → bradycardia → hypotension → fainting. Treatment includes applied tension (tensing large muscle groups to prevent blood pressure drop during exposure).

Social Anxiety Disorder (SAD)

Prevalence ~7%, with typical onset in mid-adolescence. SAD is one of the most common anxiety disorders and is associated with significant educational underachievement, occupational impairment, and social isolation. The performance only specifier (DSM-5) applies when fear is restricted to performing or speaking in public.

Clark and Wells’ (1995) cognitive model proposes a maintenance cycle with several components: (1) anticipatory processing — excessive worry before social events, rehearsing past failures; (2) self-focused attention during social situations — shifting attention inward to monitor one’s own anxiety symptoms, which paradoxically increases awareness of anxiety and reduces attention to positive social cues; (3) use of safety behaviours (e.g., avoiding eye contact, rehearsing sentences mentally, gripping objects to hide trembling) that prevent disconfirmation of feared outcomes; and (4) post-event rumination — detailed, negative review of social encounters after they occur, selectively attending to perceived mistakes.

Treatment: CBT (exposure to feared social situations + cognitive restructuring of negative social beliefs + attention training away from self-focus + dropping safety behaviours) is the gold standard. SSRIs/SNRIs for pharmacotherapy; MAOIs (phenelzine) are effective but rarely used due to dietary restrictions and side effects.

Panic Disorder and Agoraphobia

A panic attack is a sudden surge of intense fear with ≥4 of 13 somatic/cognitive symptoms:

• Palpitations or accelerated heart rate
• Sweating
• Trembling or shaking
• Shortness of breath (dyspnea)
• Feelings of choking
• Chest pain or discomfort
• Nausea or abdominal distress
• Dizziness, unsteadiness, or faintness
• Chills or hot flushes
• Numbness or tingling (paresthesias)
• Derealization or depersonalization
• Fear of losing control or “going crazy”
• Fear of dying

Panic attacks peak within minutes (typically ~10 minutes) and are self-limiting (usually resolving within 20–30 minutes). Importantly, panic attacks are not a disorder in themselves — they are a specifier that can accompany any DSM-5 diagnosis. Panic disorder requires recurrent unexpected attacks (not triggered by an obvious cue) plus ≥1 month of persistent concern about further attacks, worry about their implications (“Am I having a heart attack?”, “Am I going insane?”), or maladaptive behavioural change (avoiding exercise, carrying medication, staying near hospitals).

Clark’s cognitive model: interoceptive cues → catastrophic misinterpretation → fear → more symptoms (vicious cycle).

Treatment for panic disorder centres on interoceptive exposure — deliberately inducing feared bodily sensations (e.g., breathing through a straw to simulate dyspnea, spinning in a chair for dizziness, running in place for elevated heart rate) to break the association between physical sensations and catastrophic interpretations. Combined with cognitive restructuring and gradual in vivo exposure, interoceptive exposure produces durable improvements in 70–80% of patients.

Agoraphobia = fear/avoidance of situations where escape is difficult or help unavailable (public transport, open spaces, enclosed places, crowds, being outside the home alone). Can occur with or without panic disorder. Agoraphobia is now classified as a separate diagnosis in DSM-5.

Generalized Anxiety Disorder (GAD)

Chronic, excessive, uncontrollable worry about multiple domains (health, finances, work, family, minor matters) for ≥6 months, with ≥3 somatic symptoms (restlessness, easy fatigue, concentration difficulty, irritability, muscle tension, sleep disturbance). GAD has the highest comorbidity rate of any anxiety disorder — the majority of individuals with GAD meet criteria for at least one other disorder (most commonly MDD, social anxiety, or another anxiety disorder).

Borkovec’s avoidance model of worry: worry is predominantly verbal-linguistic (abstract, conceptual) rather than imagistic, which suppresses emotional processing of feared content. Paradoxically, worry functions as cognitive avoidance of deeper emotional engagement — the worrier thinks about problems without fully experiencing the associated emotions, preventing emotional habituation. This emotional avoidance is negatively reinforced because it provides short-term relief from distressing imagery and somatic arousal.

Dugas’ intolerance of uncertainty (IU) model proposes that IU — defined as the tendency to find ambiguity and uncertainty distressing and unacceptable — is the core cognitive vulnerability in GAD. Individuals high in IU interpret ambiguous situations as threatening and engage in excessive worry as an attempt to reduce uncertainty. This model has led to IU-focused CBT protocols with strong empirical support.

Treatment: CBT (targeting worry behaviours, intolerance of uncertainty, and cognitive avoidance), applied relaxation (Öst), mindfulness-based approaches (MBSR, MBCT). Pharmacotherapy: SSRIs/SNRIs are first-line; buspirone (anxiolytic without sedation/dependence risk); pregabalin (approved in Europe, not North America). Benzodiazepines are effective short-term but not recommended as long-term monotherapy due to dependence risk.

Biological Bases

The fear circuit (amygdala → locus coeruleus → hypothalamus) is hyperreactive in anxiety disorders. The amygdala functions as a threat-detection hub, receiving sensory input via a fast subcortical route (thalamus → amygdala) and a slower cortical route (thalamus → cortex → amygdala). In anxiety disorders, the amygdala responds excessively to ambiguous or non-threatening stimuli, while prefrontal regulatory regions (vmPFC, dlPFC) fail to adequately dampen this response.

Three neurotransmitter systems are primarily implicated:

Buspirone is a 5-HT₁A partial agonist used for GAD. Unlike benzodiazepines, it has no sedation, no dependence risk, and no withdrawal syndrome, but it requires 2–4 weeks to take effect. Benzodiazepines (e.g., lorazepam, clonazepam) provide rapid relief but carry risks of tolerance, dependence, and rebound anxiety on discontinuation — they are best reserved for short-term or as-needed use. Beta-blockers are not FDA-approved for anxiety disorders but are widely used off-label for situational anxiety (e.g., public speaking, musical performance) because they blunt the autonomic symptoms of anxiety without affecting cognition.

Twin studies show moderate heritability across anxiety disorders (\(h^2 \approx 0.30{-}0.50\)), with genetic risk being partly shared across disorders (a general anxiety/neuroticism factor) and partly specific to individual disorders.

Chapter 5: Somatic Symptom and Related Disorders

From “Hysteria” to Functional Disorders: A Historical Perspective

Few areas of psychopathology carry a longer or more politically charged history than the disorders now classified under the somatic symptom umbrella. The concept of hysteria — from the Greek hystera (uterus) — dates to the Egyptian Kahun Papyrus (c. 1900 BCE), which attributed a range of physical symptoms to a “wandering uterus” that could migrate through the body. Hippocrates (5th century BCE) perpetuated this model, classifying hysteria as a disease of women caused by uterine displacement due to sexual deprivation. For over two millennia, the condition was linked inextricably to female biology and, by extension, to assumptions about female irrationality.

The 19th century transformed the field. Jean-Martin Charcot (1825–1893), working at the Salpêtrière Hospital in Paris, used hypnosis to induce and remove hysterical symptoms — demonstrating that they were functional (non-organic) in nature. Crucially, Charcot studied male patients as well, challenging the uterine theory, though his theatrical demonstrations have been criticised for potentially encouraging performance. His student Pierre Janet (1859–1947) proposed that hysteria resulted from dissociation — a splitting of consciousness due to psychological trauma that prevented the integration of traumatic experiences. Janet’s concept of désagrégation anticipated modern dissociation theory and is experiencing renewed interest.

Josef Breuer and Sigmund Freud, in their landmark Studies on Hysteria (1895), proposed that hysterical symptoms resulted from the conversion of repressed emotional energy into somatic form — the origin of the term “conversion disorder.” Their distinction between primary gain (the symptom keeps unconscious conflict from awareness) and secondary gain (the symptom elicits care, attention, or avoidance of responsibility) remains conceptually influential, though the psychoanalytic framework itself has limited empirical support.

The two World Wars provided powerful evidence against the gendered model of hysteria. Large numbers of soldiers — overwhelmingly male — presented with functional paralysis, blindness, tremors, and seizures under the labels “shell shock” and “war neurosis,” demonstrating that extreme stress, not uterine pathology, was the proximate cause. The mid-20th century saw the term “hysteria” gradually abandoned for its pejorative connotations and embedded gender bias, replaced by “conversion disorder” in DSM-III (1980).

The DSM-5 Reorganisation

The DSM-5 fundamentally restructured this diagnostic area. The DSM-IV category of “Somatoform Disorders” — which included somatisation disorder, undifferentiated somatoform disorder, pain disorder, and hypochondriasis — was replaced by Somatic Symptom and Related Disorders. The most significant change was eliminating the requirement that symptoms be “medically unexplained.” This criterion had been problematic on multiple grounds: it was dualistic (implying a sharp mind/body divide), unreliable (physicians often disagreed about what constituted adequate medical explanation), stigmatising (patients felt their suffering was being dismissed as imaginary), and conceptually flawed (many patients have both a genuine medical condition and an excessive psychological response to it). The new framework focuses on the presence of excessive cognitive, emotional, or behavioural responses to somatic symptoms — regardless of whether a medical explanation exists.

Somatic Symptom Disorder (SSD)

Prevalence in the general population is approximately 5–7%, rising to 5–35% in primary care settings depending on criteria stringency. Women are affected roughly twice as often as men (the gender gap was far more extreme — approximately 10:1 — under the old somatisation disorder criteria, which required 8+ symptoms across 4 body systems with onset before age 30). SSD commonly co-occurs with major depressive disorder (up to 50–70% comorbidity), anxiety disorders, and personality disorders. Genuine medical conditions frequently coexist — SSD does not require the absence of medical illness.

The cognitive-behavioural model of SSD emphasises a self-reinforcing cycle: somatosensory amplification (Barsky’s term for the tendency to perceive normal bodily sensations as intense, noxious, and disturbing) → catastrophic misinterpretation of benign somatic cues → illness behaviour reinforced by reassurance-seeking and activity avoidance → heightened emotional distress (anxiety, depression) → amplified somatic perception. Reassurance from physicians provides only transient relief and paradoxically maintains the cycle by reinforcing the belief that symptoms require medical investigation.

Biological factors include heightened physiological reactivity, HPA axis dysregulation, altered pain processing, and altered interoception — the perception of internal body states. Patients with SSD often show reduced interoceptive accuracy (poor objective ability to detect heartbeat, for example) combined with heightened interoceptive sensibility (high self-reported attention to bodily states). This mismatch — poor objective accuracy with high subjective vigilance — creates fertile ground for misinterpretation.

Psychological factors include childhood illness or parental illness modelling, trauma history (childhood abuse and neglect are robust risk factors across studies), alexithymia (difficulty identifying and expressing emotions, leading to expression of distress through somatic channels), and insecure attachment. Social and cultural factors strongly shape somatic expression: in many cultures around the world, somatic complaints are a more socially acceptable idiom of distress than psychological complaints, and lower socioeconomic status and limited health literacy are additional risk factors. Iatrogenic reinforcement — from repeated medical investigations that implicitly validate the patient’s fear that something is seriously wrong — is a significant maintaining factor.

Treatment: CBT is the best-supported treatment, with effect sizes of approximately d = 0.6–0.9 for symptom reduction. Core components include psychoeducation about the attention-symptom cycle, cognitive restructuring of catastrophic health beliefs, behavioural experiments (reducing reassurance-seeking, graded activity exposure), and attention training. Antidepressants (SSRIs and SNRIs) show modest benefit, particularly when comorbid depression or anxiety is present; SNRIs such as duloxetine and venlafaxine have additional evidence for pain reduction. Collaborative care models integrating mental health within primary care are particularly effective, as they address the reality that these patients typically present to physicians, not psychologists.

Illness Anxiety Disorder

The key distinction from SSD: in SSD, distressing somatic symptoms are prominent; in IAD, somatic symptoms are minimal or absent — the core problem is the anxiety and preoccupation with illness itself. Approximately 75% of individuals previously diagnosed with DSM-IV hypochondriasis now meet criteria for SSD (because they do have significant somatic symptoms); the remaining 25% — those with prominent health anxiety but minimal physical complaints — receive the IAD diagnosis. Community prevalence is approximately 1–5%; the gender ratio is approximately equal; and the course is chronic without treatment, with up to 50% showing persistent symptoms at 1–5 year follow-up.

The Clark and Salkovskis cognitive model of health anxiety is the dominant theoretical framework and the basis for the most effective treatment. The model identifies four components operating in a self-maintaining cycle:

1. Dysfunctional health beliefs developed through early experience: “bodily changes are always a sign of serious disease,” “if I don’t worry about my health, something bad will happen”
2. Critical triggering incident (health-relevant information — a news story, a friend’s diagnosis, a novel symptom) that activates these beliefs
3. Catastrophic misinterpretation of normal bodily sensations or health information as evidence of serious illness
4. Four maintaining processes: (a) physiological arousal from the anxiety itself produces more symptoms to misinterpret (positive feedback loop); (b) selective attention to the body discovers more “evidence”; (c) safety behaviours (checking, reassurance-seeking, avoidance) prevent disconfirmation of the catastrophic belief; and (d) cognitive biases (confirmation bias, probability overestimation) filter information to support the feared interpretation

CBT based on this model is the gold-standard treatment, with large effect sizes (d = 1.0–1.5 vs. waitlist; d = 0.6–0.8 vs. active controls). The pivotal trial by Tyrer et al. (2014; N = 444) demonstrated a number needed to treat (NNT) of 3 for clinically significant improvement, with benefits maintained at two-year follow-up and significant cost savings from reduced medical utilisation. SSRIs also show efficacy (supporting the OCD-spectrum conceptualisation of health anxiety), and internet-delivered CBT has shown promising results with effect sizes comparable to face-to-face therapy.

Conversion Disorder (Functional Neurological Symptom Disorder)

FND is remarkably common in neurology: approximately 5–16% of outpatient neurology referrals, and PNES account for 5–20% of patients referred to epilepsy clinics. Incidence is approximately 4–12 per 100,000 per year, with a gender ratio of approximately 2–3:1 female-to-male (varying by symptom type). Co-occurrence with depression (up to 50%), anxiety disorders (up to 45%), PTSD, and dissociative disorders is common. Notably, 10–20% of patients with PNES also have genuine epilepsy — the conditions are not mutually exclusive.

Positive neurological signs are now central to diagnosis. Hoover’s sign demonstrates that a patient with functional leg weakness shows involuntary hip extension when flexing the contralateral hip (proving the motor pathway is intact) even though voluntary hip extension appears “weak.” Tremor entrainment shows that a functional tremor changes frequency or stops when the patient performs rhythmic movements with the other hand — an impossibility in organic tremor. For PNES, EEG during an event shows no epileptiform activity, and the events display features atypical for epilepsy (eyes closed, prolonged duration, waxing and waning, side-to-side head movement).

The predictive processing model (Edwards, Adams, Brown, Pareés, & Friston, 2012) is the leading contemporary neuroscientific framework. It conceptualises FND as a disorder in which aberrant top-down predictions about body state (e.g., “my arm is paralysed”) override bottom-up sensory and motor signals. These predictions are held with high precision (strong conviction), making them resistant to contradictory evidence, and they operate below the level of conscious intention — which is why patients genuinely experience the symptoms as involuntary. Neuroimaging studies consistently show altered functional connectivity between prefrontal/limbic regions and motor cortex: the motor cortex may be intact but its activation is modulated (inhibited) by emotional processing regions. Heightened amygdala–motor cortex coupling suggests that emotional processing directly influences motor output.

This model elegantly unifies conversion symptoms, dissociation, and placebo/nocebo effects within a common computational framework, and it explains why symptoms are “real” (the brain genuinely generates the experience of paralysis or tremor) even though the peripheral nervous system is structurally intact.

Treatment is multidisciplinary. The critical first step is transparent diagnosis delivery — explaining what the condition is (a problem with how the nervous system functions, not a problem with the hardware) rather than merely what it is not. Showing patients their own Hoover’s sign or tremor entrainment can be therapeutically powerful. Specialised physiotherapy is the best-supported treatment for motor FND, with principles including demonstrating that normal movement is possible, retraining automatic rather than voluntary movement, and reducing attention to the affected limb. CBT adapted for FND shows moderate evidence. For PNES, the CODES trial (Goldstein et al., 2020, Lancet Psychiatry) found that CBT reduced seizure frequency and improved psychosocial functioning, though the rate of complete seizure freedom was not significantly better than standard medical care.

Factitious Disorder

The distinction from malingering is critical: in factitious disorder, the motivation is to assume the sick role (internal, psychological gain — to be nurtured, cared for, to occupy the identity of a patient). In malingering, the motivation is external incentive (financial compensation, avoiding legal consequences, obtaining drugs). Malingering is not a mental disorder in DSM-5-TR but rather a V/Z code (a condition that may be a focus of clinical attention). In practice, the boundary is often blurry, and mixed motivations are common.

The most severe, chronic form — Munchausen syndrome — is characterised by peregrination (travelling to different hospitals), pseudologia fantastica (elaborate false medical histories), and repeated hospitalisations. Prevalence is very difficult to estimate given that deception is inherent to the condition, but factitious disorder imposed on self is estimated at approximately 1% of hospital patients. Factitious Disorder Imposed on Another is estimated at approximately 0.5–2 per 100,000 children under age 1, with a mortality rate in identified cases of 6–10% — making it a serious form of child abuse with mandatory reporting obligations.

Treatment is extremely challenging because patients typically deny the behaviour and disengage. Supportive, non-confrontational approaches may be more effective than direct confrontation. No well-controlled treatment studies exist.

Psychological Factors Affecting Other Medical Conditions

This DSM-5-TR diagnosis captures the well-established bidirectional relationship between psychological states and physical health — when psychological or behavioural factors adversely affect the course, treatment, or pathophysiology of a genuine medical condition.

The evidence for mind-body interaction is extensive. Depression increases post-myocardial infarction mortality by approximately 2–3 times (Frasure-Smith et al., landmark studies). Chronic stress suppresses cellular immunity — reducing natural killer cell activity, impairing T-cell proliferation, and slowing wound healing (Kiecolt-Glaser’s programme of psychoneuroimmunology research). The adverse childhood experiences (ACEs) literature demonstrates a dose-response relationship between childhood adversity and adult health outcomes across cardiovascular disease, autoimmune conditions, chronic pain, and early mortality. And a meta-analysis by Holt-Lunstad and colleagues found that loneliness and social isolation carry a mortality risk comparable to smoking 15 cigarettes per day.

These findings underscore the integrative principle at the heart of the biopsychosocial model: psychological and biological processes are not merely parallel — they are mechanistically intertwined through the HPA axis, the autonomic nervous system, inflammatory pathways, and health behaviours.

Chapter 6: Obsessive–Compulsive and Related Disorders

OCD

Prevalence ~2%, with equal gender distribution (unlike anxiety disorders, where females predominate). Mean age of onset is ~19–20 years, though childhood onset is not uncommon (particularly in males). The ego-dystonic quality of obsessions is a defining feature — the person recognises that the thoughts are a product of their own mind and finds them repugnant, distressing, or nonsensical. This distinguishes obsessions from overvalued ideas (held with less resistance, as in BDD) and delusions (held with fixed conviction). However, insight exists on a spectrum: DSM-5 includes specifiers for OCD “with good or fair insight,” “with poor insight,” and “with absent insight/delusional beliefs.”

Common obsessional themes and their associated compulsions:

Salkovskis’ cognitive model: intrusive thoughts are universal (research shows ~90% of the general population experiences intrusive thoughts similar in content to clinical obsessions), but people with OCD appraise them as personally significant and morally blameworthy, leading to neutralization (compulsions) that paradoxically increase intrusion frequency.

Several cognitive distortions maintain OCD:

• Inflated responsibility: “If I don’t check the stove, the house will burn down, and it will be my fault.”
• Thought–action fusion (TAF): the belief that thinking about an event makes it more likely to happen (likelihood TAF) or that having a thought is morally equivalent to performing the action (moral TAF). For instance, a person who has an intrusive image of harming a child believes this thought makes them as morally culpable as someone who actually harmed a child.
• Overestimation of threat: exaggerated assessment of the probability and severity of negative outcomes.
• Intolerance of uncertainty: an inability to accept that certainty is unattainable (e.g., “I must be 100% sure the door is locked”).
• Perfectionism: the belief that mistakes are catastrophic and that a perfect state is both possible and necessary.

Treatment: ERP (Exposure and Response Prevention) — gold-standard behavioural intervention. In ERP, patients work with the therapist to construct an exposure hierarchy — a ranked list of feared situations ordered by subjective units of distress (SUDS, 0–100). Treatment proceeds gradually from lower-ranked to higher-ranked items. During exposure, the patient confronts the obsessional trigger (e.g., touching a “contaminated” doorknob) while preventing the compulsive response (e.g., not washing hands). Through prolonged and repeated exposure, habituation occurs — anxiety diminishes naturally without the compulsion. Approximately 60–70% of patients show significant improvement with ERP.

Pharmacotherapy for OCD involves SSRIs at higher doses than used for depression (e.g., fluoxetine 40–80 mg vs. 20 mg for depression) or clomipramine (a tricyclic antidepressant with strong serotonergic activity). Combination of ERP + SSRI is often superior to either alone.

Neuroimaging and Neurobiology of OCD

Neuroimaging studies consistently implicate a hyperactive cortico-striato-thalamo-cortical (CSTC) loop, particularly involving the orbitofrontal cortex (OFC), caudate nucleus, and thalamus. The OFC is involved in error detection and threat appraisal; hyperactivity here may generate the persistent feeling that “something is wrong.” The caudate normally acts as a gating mechanism, filtering irrelevant signals. When this gating fails, the thalamus is overactivated, sending signals back to the OFC in a self-reinforcing cycle. Successful treatment with either ERP or SSRIs normalises activity in this circuit.

For treatment-resistant OCD (failure of adequate trials of multiple SSRIs, clomipramine, and ERP), neurosurgical and neuromodulatory options are available. Deep brain stimulation (DBS) — involving surgical implantation of electrodes in the ventral capsule/ventral striatum — has received humanitarian device exemption from the FDA. DBS produces clinically meaningful improvement in approximately 50–60% of treatment-resistant patients. Transcranial magnetic stimulation (TMS) targeting the supplementary motor area or OFC has also been FDA-cleared for OCD.

OCD-Spectrum Disorders

The DSM-5 groups related conditions in the OCD chapter:

• Body Dysmorphic Disorder (BDD): preoccupation with perceived defect(s) in physical appearance that are not observable or appear slight to others, accompanied by repetitive behaviours (mirror-checking, excessive grooming, skin picking, reassurance seeking) or mental acts (comparing appearance with others). Prevalence ~2%; high comorbidity with MDD and social anxiety. The muscle dysmorphia variant involves preoccupation with being insufficiently lean/muscular, more common in males. BDD responds to CBT (exposure + response prevention) and SSRIs.
• Hoarding Disorder: persistent difficulty discarding possessions regardless of their actual value, due to perceived need to save items or distress associated with discarding. This results in accumulation that congests living areas and substantially compromises their intended use. Prevalence ~2–6%, increasing with age. Hoarding disorder has distinct neural correlates from OCD — neuroimaging shows abnormal activity in the anterior cingulate cortex and insula (regions involved in decision-making and emotional attachment to objects). Standard OCD treatments (ERP, SSRIs) are less effective for hoarding; specialised CBT for hoarding addresses motivational issues, organisational skills, and gradual discarding with in-home sessions.
• Trichotillomania (Hair-Pulling Disorder): recurrent pulling of one’s hair resulting in hair loss, with repeated attempts to decrease or stop; prevalence ~1–2%. Excoriation (Skin-Picking) Disorder: recurrent picking of one’s skin resulting in lesions. Both are body-focused repetitive behaviours (BFRBs) — they share features with both OCD (repetitive behaviours) and addictive disorders (urge-based, tension-relief pattern). Treatment: habit reversal training (HRT), stimulus control strategies, and in some cases N-acetylcysteine (a glutamate modulator).

Chapter 7: Mood Disorders

Major Depressive Disorder (MDD)

12-month prevalence ~7%; 2:1 female-to-male ratio. Specifiers include: with anxious distress, melancholic features, psychotic features, peripartum onset, seasonal pattern.

Seasonal Affective Disorder (SAD)

The seasonal pattern specifier (commonly called SAD) describes recurrent depressive episodes with a regular temporal relationship to a particular season — most often winter. The prevailing biological model involves reduced light exposure → disrupted circadian rhythms and altered melatonin/serotonin metabolism. Light therapy (10,000 lux bright light box for 30 minutes each morning) is an effective first-line treatment, with response rates comparable to antidepressant medication. CBT adapted for SAD has also demonstrated efficacy, particularly in preventing recurrence across subsequent winters.

Peripartum Depression

The peripartum onset specifier applies when a depressive episode begins during pregnancy or within 4 weeks postpartum (though clinical convention often extends this to the first year). Peripartum depression affects approximately 10–15% of birthing parents and can include severe anxiety, intrusive thoughts of harming the infant, and impaired mother–infant bonding. Risk factors include history of depression, lack of social support, unplanned pregnancy, and hormonal fluctuations. Untreated peripartum depression can have lasting effects on infant cognitive and emotional development. Treatment includes psychotherapy (IPT has particularly strong evidence), SSRIs (with risk–benefit analysis for breastfeeding), and in severe cases, the novel neurosteroid brexanolone (an IV formulation of allopregnanolone, FDA-approved in 2019).

Biological factors: the monoamine hypothesis (↓ serotonin, NE, dopamine) was the earliest biological model but is now considered an oversimplification. HPA axis dysregulation (hypercortisolism, elevated CRF) is well-documented; structural changes include ↓ hippocampal volume (neurogenesis impairment) and reduced PFC activity. Inflammatory processes (elevated IL-6, TNF-α) are increasingly implicated. Genetic heritability \(h^2 \approx 0.37\).

Psychological theories:

• Beck’s cognitive triad: negative views of self, world, and future; maintained by cognitive distortions (all-or-nothing thinking, catastrophizing, overgeneralisation).
• Hopelessness theory (Abramson): stable, global, internal attribution for negative events → hopelessness → depression.
• Rumination theory (Nolen-Hoeksema): rumination — repetitive, passive focus on symptoms, causes, and consequences of depression — maintains and exacerbates depressive episodes. The Response Styles Theory proposes that women’s higher rates of rumination partly explain the gender difference in depression prevalence. Distraction and problem-solving are adaptive alternatives.
• Behavioural activation model: reduced reinforcement → withdrawal → further reduced reinforcement (downward spiral). Behavioural activation (BA) therapy directly targets this cycle by scheduling valued activities to restore reinforcement.
• Interpersonal theory: depression is linked to disrupted interpersonal functioning — grief, role transitions, role disputes, and interpersonal deficits. Interpersonal Therapy (IPT) addresses one or two of these problem areas in a time-limited (12–16 session) format.

Treatment: CBT, behavioural activation, IPT; SSRIs/SNRIs; severe or treatment-resistant cases → ECT (electroconvulsive therapy) or TMS (transcranial magnetic stimulation).

ECT involves brief, controlled electrical stimulation of the brain under general anaesthesia, inducing a generalized seizure. Despite its stigmatised history, modern ECT is the most effective acute treatment for severe depression, with response rates of 70–90%. It is particularly indicated for treatment-resistant depression, severe suicidality, psychotic depression, and catatonia. Cognitive side effects (anterograde and retrograde amnesia) are the primary concern; unilateral electrode placement and ultra-brief pulse widths have reduced memory disruption.

TMS uses focused magnetic pulses to stimulate the left dorsolateral PFC (hypoactive in depression). Repetitive TMS (rTMS) is FDA-cleared for treatment-resistant MDD and is non-invasive, requiring no anaesthesia. Response rates are lower than ECT (~50–60%) but the side-effect profile is favourable. Ketamine (an NMDA receptor antagonist) and its enantiomer esketamine (FDA-approved as a nasal spray in 2019) represent a novel approach, producing rapid antidepressant effects within hours — a breakthrough for acutely suicidal patients who cannot wait weeks for SSRIs to take effect. The mechanism likely involves enhanced glutamatergic signalling and rapid synaptogenesis via the mTOR pathway.

Persistent Depressive Disorder (Dysthymia)

Depressed mood more days than not for ≥2 years (adults; ≥1 year in children/adolescents), with ≥2 additional symptoms (appetite change, sleep disturbance, low energy, low self-esteem, poor concentration, hopelessness). Less severe but more chronic than MDD; the individual often cannot recall a time when they felt genuinely well. High rates of double depression (MDD superimposed on PDD) — the chronic low-grade depression periodically deepens into full MDD episodes and then returns to the dysthymic baseline. This pattern is associated with poorer treatment response and higher relapse rates than MDD alone. CBT, CBASP (Cognitive Behavioural Analysis System of Psychotherapy), and antidepressant medication are evidence-based treatments.

Bipolar Disorders

Heritability \(h^2 \approx 0.75{-}0.93\) — among the highest in psychiatry. The kindling model posits that early episodes sensitize the brain to future episodes, such that later episodes may be triggered by progressively less stress or may occur spontaneously.

Rapid cycling is a specifier applied when ≥4 mood episodes occur within a 12-month period. It affects approximately 10–20% of bipolar patients, is more common in Bipolar II and in women, and is associated with poorer treatment response. Mixed episodes (now captured in DSM-5 as the “with mixed features” specifier) involve simultaneous manic and depressive symptoms — for example, a patient may feel intensely energized and agitated while also experiencing hopelessness and suicidality. Mixed features carry an elevated suicide risk compared to pure mania or pure depression.

Lithium remains the first-line mood stabilizer. Its mechanism is not fully understood but involves modulation of second-messenger systems (inositol depletion, GSK-3β inhibition) and neuroprotective effects (increased grey matter volume, enhanced BDNF). Lithium has a narrow therapeutic index — blood levels must be carefully monitored (target: 0.6–1.2 mEq/L) to avoid toxicity (tremor, renal impairment, thyroid dysfunction). Despite these challenges, lithium is the only mood stabilizer with demonstrated anti-suicidal properties. Alternatives include valproate (especially for rapid cycling and mixed states), lamotrigine (particularly effective for bipolar depression prevention), and atypical antipsychotics (quetiapine, lurasidone). Psychoeducation and CBT reduce relapse by improving medication adherence and early warning sign recognition.

Suicide

Suicide is a major public health concern and the leading cause of death in psychiatric populations. In Canada, approximately 4,500 people die by suicide annually, and for every completed suicide there are an estimated 20–25 attempts. Suicide rates are disproportionately high among Indigenous peoples, LGBTQ+ youth, and middle-aged men.

Risk factors include: prior suicide attempt (the single strongest predictor), hopelessness, social isolation, substance use, male sex, access to lethal means, chronic pain, recent loss, and family history of suicide. Protective factors include strong social connections, reasons for living, cultural or religious beliefs against suicide, and access to effective mental health care.

Means restriction (e.g., bridge barriers, firearm storage laws, medication packaging limits, detoxification of domestic gas) is one of the most effective suicide prevention strategies, because many suicidal crises are temporary — removing access to lethal means during the crisis period saves lives, and most individuals who survive an attempt do not go on to die by suicide. Clinical assessment uses structured tools such as the Columbia Suicide Severity Rating Scale (C-SSRS), which distinguishes wish to be dead, suicidal ideation, ideation with intent, ideation with plan, and actual behaviour.

Chapter 8: Trauma- and Stressor-Related Disorders

PTSD

Lifetime prevalence ~6.8% in the general population; rates are substantially higher in specific populations: ~10–30% of combat veterans, ~33–45% of sexual assault survivors, and ~15–20% of first responders. Women are approximately twice as likely as men to develop PTSD following trauma exposure, despite lower overall trauma exposure rates — suggesting greater vulnerability possibly related to trauma type (interpersonal violence), biological factors (hormonal influences on fear conditioning), and peritraumatic dissociation.

Only ~20% of trauma-exposed individuals develop PTSD — resilience is the modal outcome. Risk factors for developing PTSD after trauma include: prior trauma exposure, pre-existing mental health conditions, peritraumatic dissociation, lack of social support, severity and duration of trauma, and perceived life threat. Protective factors include strong social support, active coping strategies, and post-trauma psychological first aid.

Symptom Clusters (DSM-5):

Biological: amygdala hyperreactivity, medial PFC hypoactivity, hippocampal atrophy, and — paradoxically — low cortisol (the “cortisol paradox”). Unlike depression, where cortisol is typically elevated, PTSD is associated with enhanced negative feedback sensitivity of the HPA axis, resulting in lower baseline cortisol. This pattern may reflect a pre-existing vulnerability or an adaptation to chronic stress that sensitises the stress response system, amplifying the fear response to trauma reminders despite low tonic cortisol.

Ehlers & Clark’s cognitive model: the trauma memory is poorly elaborated/contextualized, leading to a sense of current threat; idiosyncratic appraisals of the trauma (e.g., “nowhere is safe,” “I am permanently damaged”) maintain PTSD.

Complex PTSD and Related Concepts

The ICD-11 introduced Complex PTSD (C-PTSD) as a distinct diagnosis for individuals exposed to prolonged, repeated, or inescapable trauma — typically childhood abuse, domestic violence, or captivity (e.g., prisoners of war, trafficking survivors). C-PTSD includes the core PTSD symptom clusters plus three additional features collectively termed disturbances in self-organization (DSO): affect dysregulation (explosive anger or emotional numbing), negative self-concept (pervasive shame, guilt, or worthlessness), and disturbed relationships (difficulty trusting others, patterns of revictimization or avoidance). The DSM-5-TR does not include C-PTSD as a separate diagnosis but captures many of these features through specifiers and comorbid conditions.

Moral injury is a related concept that has gained prominence in military and first-responder populations. It refers to the psychological distress that results from actions (or failures to act) that violate one’s moral code — for example, a soldier who harmed a civilian during combat, or a paramedic who could not save a child. Moral injury overlaps with PTSD but is characterised more by shame, guilt, and existential crisis than by fear-based symptoms.

Intergenerational trauma (also called historical or transgenerational trauma) refers to the transmission of trauma effects across generations. This has been documented in Indigenous communities affected by residential schools and colonisation, Holocaust survivor families, and descendants of enslaved peoples. Mechanisms may include epigenetic changes, disrupted parenting, family narratives, and ongoing structural disadvantage.

PTSD in Specific Populations

Military veterans and first responders face elevated PTSD prevalence due to repeated trauma exposure. Approximately 11–20% of veterans of Operations Iraqi Freedom and Enduring Freedom develop PTSD. Barriers to treatment include stigma, concerns about career impact, and a military culture that emphasises toughness. Evidence-based treatments (PE, CPT) are effective in military populations, but dropout rates can be high.

Prolonged Grief Disorder

PGD is distinguished from normal grief by its intensity, duration, and associated functional impairment. It is also distinct from MDD, although the two frequently co-occur. Treatment approaches include complicated grief treatment (CGT), which integrates elements of CBT with interpersonal therapy and motivational interviewing techniques.

Treatments for PTSD: Prolonged Exposure (PE) and Cognitive Processing Therapy (CPT) have the strongest evidence. EMDR (Eye Movement Desensitization and Reprocessing) is effective (mechanism debated — it may work through exposure rather than eye movements per se). Pharmacotherapy: SSRIs (sertraline, paroxetine are FDA-approved for PTSD). Prazosin (an alpha-1 adrenergic antagonist) has been used for trauma-related nightmares, though recent large trials have produced mixed results.

Acute Stress Disorder

Same symptom profile as PTSD but duration is 3 days to 1 month post-trauma. Dissociative symptoms are more prominent. Strong predictor of subsequent PTSD.

Adjustment Disorders

Emotional/behavioural symptoms in response to an identifiable stressor (e.g., divorce, job loss, medical diagnosis, academic failure), disproportionate to its severity, developing within 3 months of the stressor’s onset. Subtypes include: with depressed mood, with anxiety, with mixed anxiety and depressed mood, with disturbance of conduct, and with mixed disturbance of emotions and conduct. The diagnosis does not meet criteria for another specific disorder and symptoms resolve within 6 months after the stressor (or its consequences) has terminated. Adjustment disorders are among the most commonly diagnosed conditions in clinical practice, accounting for ~5–20% of outpatient mental health visits. Often self-limiting; brief, problem-focused psychotherapy is effective.

Reactive Attachment Disorder / Disinhibited Social Engagement Disorder

Develop in children following severe neglect or institutional rearing; both reflect fundamental disruption of attachment systems, but with opposite behavioural presentations. RAD is characterised by inhibited, emotionally withdrawn behaviour — the child rarely seeks or responds to comfort from caregivers, shows minimal social/emotional responsiveness, and may display episodes of unexplained irritability or sadness. DSED involves indiscriminate, disinhibited social behaviour — the child approaches and interacts with unfamiliar adults without appropriate social boundaries, shows willingness to go off with strangers, and does not check back with caregivers in unfamiliar settings. Importantly, DSED can persist even after placement in a nurturing environment, whereas RAD typically improves with stable, responsive caregiving. Both disorders require evidence of pathogenic care (neglect, institutional rearing, or repeated changes of primary caregiver) as a diagnostic prerequisite.

Chapter 9: Eating Disorders & Sleep–Wake Disorders

Anorexia Nervosa (AN)

Prevalence ~0.9% in women; female-to-male ~10:1. AN has the highest mortality of any psychiatric disorder (\(\approx 5{-}10\%\) per decade). The standardised mortality ratio is approximately 5.9 (nearly 6× expected death rate), and the suicide rate among individuals with AN is approximately 18 times that of age-matched peers. Causes of death include cardiac arrhythmia (from electrolyte imbalances), organ failure, and suicide. Subtypes: restricting vs. binge-eating/purging.

Medical complications of AN are extensive: bradycardia, hypotension, osteoporosis, lanugo hair, amenorrhoea, renal dysfunction, and cognitive impairment from malnutrition. Refeeding syndrome (dangerous shifts in electrolytes when nutrition is reintroduced too rapidly) can be life-threatening and requires careful medical monitoring.

Avoidant/Restrictive Food Intake Disorder (ARFID)

ARFID differs fundamentally from AN: there is no drive for thinness or distorted body image. Instead, food avoidance is driven by sensory sensitivity (e.g., to textures, colours, or smells), lack of interest in eating, or fear of aversive consequences (e.g., choking, vomiting). It is most commonly diagnosed in children and adolescents but can persist into adulthood. ARFID is particularly common in individuals with autism spectrum disorder, given the sensory processing differences associated with ASD.

Bulimia Nervosa (BN)

Recurrent episodes of binge eating (large amounts + loss of control) followed by compensatory behaviours (purging, laxatives, fasting, exercise) ≥1×/week for ≥3 months. Self-evaluation is unduly influenced by weight/shape — this cognitive feature (the overvaluation of shape and weight) is considered the core psychopathology shared by AN and BN. Prevalence ~1.5% in women. Unlike AN, individuals with BN typically maintain a normal or slightly above-normal body weight, which can delay diagnosis.

Physical signs and complications of BN include:

• Russell’s sign: calluses on the knuckles from self-induced vomiting
• Parotid gland enlargement (“chipmunk cheeks”): from repeated vomiting
• Dental erosion: stomach acid dissolves tooth enamel (perimolysis)
• Electrolyte imbalances: particularly hypokalaemia from purging → risk of cardiac arrhythmias
• Oesophageal tears (Mallory-Weiss tears) or, rarely, rupture (a medical emergency)
• Metabolic alkalosis from purging or metabolic acidosis from laxative abuse

Binge Eating Disorder (BED)

Recurrent binges without regular compensatory behaviours. Most prevalent eating disorder (~3.5% women, ~2% men). Associated with obesity but distinct from it — not all individuals with BED are obese, and most obese individuals do not have BED.

Epidemiology of Eating Disorders

Eating disorders are more common than previously recognised. Research suggests that approximately 13% of adolescents will experience at least one eating disorder by age 20. While eating disorders disproportionately affect young women, they occur across all genders, ages, ethnicities, and socioeconomic levels. Rates are rising among males (particularly for muscle dysmorphia and BED) and in non-Western countries undergoing rapid cultural change.

Treatment of Eating Disorders

CBT (particularly CBT-Enhanced, or CBT-E) is the first-line treatment for BN and BED. CBT-E addresses the core psychopathology — the overvaluation of shape and weight and their control — through a structured protocol involving self-monitoring, regular eating, cognitive restructuring, and relapse prevention. IPT is an effective alternative for BN, with outcomes comparable to CBT at long-term follow-up, though improvement is slower.

Family-Based Treatment (FBT), also known as the Maudsley method, is the preferred approach for adolescent AN. In Phase 1, parents take full control of refeeding (the adolescent does not choose what or how much to eat). In Phase 2, control is gradually returned to the adolescent. In Phase 3, the focus shifts to normal adolescent developmental issues. FBT achieves full weight restoration in 50–60% of adolescents, with outcomes superior to individual therapy for this age group. The approach works because it mobilises the family as a resource rather than blaming parents for the disorder.

For adults with AN, no single treatment has demonstrated clear superiority. Options include CBT-E, the Specialist Supportive Clinical Management (SSCM) approach, and focal psychodynamic therapy. Contingency management (e.g., making privileges contingent on weight gain in inpatient settings) has been used but raises ethical concerns about patient autonomy. Pharmacotherapy plays a limited role in AN; no medication has been shown to improve core symptoms. For BN, fluoxetine (60 mg) is the only FDA-approved medication. For BED, lisdexamfetamine is approved.

Biological and Psychological Factors

Serotonin dysfunction is implicated in AN and BN — 5-HT disturbances may contribute to perfectionism, rigidity, and mood dysregulation. Neuroimaging studies show altered reward processing in the insula and striatum in AN patients, who show reduced hedonic response to food but increased activation to images of underweight bodies and exercise cues.

Restraint theory (Herman & Polivy): dietary restraint → disinhibition → bingeing. When rigid dietary rules are inevitably broken (even slightly), the individual abandons restraint entirely (“I’ve already blown it”) in a pattern called the abstinence violation effect.

Sociocultural and Psychological Risk Factors

Thin-ideal internalization — the extent to which an individual adopts the culturally promoted thin body ideal as a personal standard — is one of the strongest risk factors for eating disorders. Social media use has intensified this risk: appearance-focused platforms (e.g., Instagram, TikTok) promote upward social comparison, exposure to idealised body images, and “fitspiration” or “thinspiration” content. Experimental studies show that even brief exposure to idealised images on social media increases body dissatisfaction, particularly among young women.

Ethnic and cultural differences in eating disorders are important. Historically, eating disorders were considered primarily afflictions of White, affluent women — a misconception that has delayed diagnosis in other groups. Research now shows that Black, Indigenous, and Latinx individuals develop eating disorders at comparable or higher rates but are significantly less likely to be screened or diagnosed. BED in particular shows relatively equal prevalence across ethnic groups.

Perfectionism (especially self-oriented and socially prescribed perfectionism) is a well-documented risk factor for AN, where it manifests as rigid dietary rules, exercise compulsivity, and intolerance of weight gain. Family dynamics — including enmeshment, overprotection, conflict avoidance, and parental emphasis on weight and appearance — were historically emphasised by Minuchin’s family systems model. While the theory that families “cause” eating disorders is no longer accepted, family factors clearly contribute to risk and maintenance.

Heritability: AN \(h^2 \approx 0.48{-}0.74\), BN \(h^2 \approx 0.55\), BED \(h^2 \approx 0.41{-}0.57\). Recent GWAS studies have identified that AN is genetically correlated not only with other psychiatric disorders but also with metabolic traits (e.g., low BMI, low insulin resistance), suggesting it is both a psychiatric and a metabolic disorder.

Sleep–Wake Disorders

Obstructive Sleep Apnea (OSA): repeated upper airway collapse during sleep → arousals → daytime somnolence. OSA is extremely prevalent (~10–30% of adults) and is associated with hypertension, cardiovascular disease, stroke, type 2 diabetes, and motor vehicle accidents due to daytime sleepiness. Risk factors include obesity, male sex, advancing age, craniofacial anatomy (retrognathia, large tongue), and neck circumference >17 inches. Diagnosis is confirmed by polysomnography (sleep study) showing ≥5 obstructive apneas or hypopneas per hour of sleep (apnea-hypopnea index, AHI ≥5). Treatment: CPAP (Continuous Positive Airway Pressure) is the gold standard — a mask worn during sleep delivers pressurised air to keep the airway open. Alternatives include oral appliances, positional therapy, weight loss, and in selected cases, upper airway surgery (uvulopalatopharyngoplasty).

Circadian rhythm disorders (e.g., delayed sleep phase) reflect misalignment of the internal clock — governed by the suprachiasmatic nucleus (SCN) of the hypothalamus — with environmental demands. The SCN synchronises to light/dark cycles via retinal input. Melatonin, secreted by the pineal gland in response to darkness, signals sleep onset. Circadian disruptions are common among shift workers, travellers (jet lag), and adolescents (whose circadian rhythms naturally shift later, creating a mismatch with early school start times).

Sleep Hygiene

While sleep hygiene alone is generally insufficient to treat clinical insomnia, it forms the foundation of all behavioural sleep interventions and is an important component of psychoeducation.

Parasomnias: NREM disorders (sleepwalking, night terrors — typically in slow-wave sleep) vs. REM sleep behaviour disorder (RBD) — acting out dreams due to loss of normal REM atonia. RBD is strongly associated with alpha-synucleinopathies: approximately 80–90% of individuals with idiopathic RBD will eventually develop Parkinson’s disease, Lewy body dementia, or multiple system atrophy, making it one of the strongest prodromal markers for these neurodegenerative conditions.

CBT-I (Cognitive Behavioural Therapy for Insomnia) is the first-line treatment for insomnia, superior to pharmacotherapy long-term. CBT-I is a structured, typically 6–8 session protocol with the following core components:

CBT-I produces durable improvements that persist long after treatment ends, unlike hypnotic medications (e.g., zolpidem, eszopiclone) which lose efficacy upon discontinuation and carry risks of dependence and next-day impairment.

Chapter 10: Personality Disorders

Overview

Personality disorders are among the most prevalent psychiatric conditions (overall prevalence ~10–15% in the general population) and among the most challenging to treat. They are defined by their ego-syntonic nature — in many cases, the person does not perceive their personality traits as problematic, experiencing them as “just who I am” rather than as symptoms. This contrasts with most Axis I disorders, which are ego-dystonic (experienced as unwanted and distressing). This distinction has important treatment implications: motivation for change is often lower, and therapeutic alliance is more difficult to establish.

Personality disorders typically emerge in adolescence or early adulthood and, by definition, represent stable patterns rather than episodic conditions. However, longitudinal research (e.g., the CLPS study) has shown that personality disorder symptoms are more dynamic than previously assumed — many patients show significant improvement over years, particularly in acute symptoms like self-harm and impulsivity, while more temperamental features (chronic emptiness, identity disturbance) tend to be more persistent.

DSM-5 lists 10 PDs in three clusters:

Borderline Personality Disorder (BPD)

Prevalence ~1.6% in the general population (higher in clinical settings: ~10% of psychiatric outpatients, ~20% of inpatients). Pervasive instability of interpersonal relationships, self-image, affect, and impulse control. Core features include: frantic efforts to avoid abandonment (real or imagined), splitting (idealization/devaluation — alternating between viewing others as all-good and all-bad), identity disturbance (unstable self-image or sense of self), impulsivity in at least two areas (spending, sex, substance use, binge eating, reckless driving), recurrent self-harm and suicidality (approximately 75% of BPD patients engage in self-harm; 8–10% die by suicide), affective instability (rapid, intense mood shifts lasting hours to days), chronic feelings of emptiness, inappropriate intense anger, and transient stress-related paranoid ideation or dissociation.

Linehan’s biosocial model: biologically based emotional sensitivity × invalidating environment → failure to develop emotion regulation skills. Treatment: DBT (Dialectical Behaviour Therapy) — skills training (mindfulness, distress tolerance, emotion regulation, interpersonal effectiveness) + individual therapy. DBT is the most extensively researched treatment for BPD and has demonstrated efficacy in reducing self-harm, suicidal behaviour, and hospitalisation.

Additional evidence-based treatments for BPD include:

• Schema Therapy (Young): identifies and modifies early maladaptive schemas (deeply held beliefs about self and others, such as abandonment, defectiveness, or emotional deprivation) and schema modes (moment-to-moment emotional states like the “vulnerable child” or “punitive parent” mode). Schema therapy integrates cognitive, experiential, and limited reparenting techniques. RCTs show it is as effective as DBT for BPD.
• Mentalization-Based Treatment (MBT) (Bateman & Fonagy): based on attachment theory, MBT targets mentalizing — the capacity to understand behaviour in terms of underlying mental states (thoughts, feelings, desires, intentions) in oneself and others. Individuals with BPD often lose mentalizing capacity under emotional stress, leading to misinterpretation of others’ intentions and reactive, impulsive behaviour. MBT aims to strengthen mentalizing through a curious, non-knowing therapeutic stance.
• Transference-Focused Psychotherapy (TFP) (Kernberg): a psychodynamic approach that uses the therapeutic relationship to explore and modify the patient’s internal representations (object relations) of self and other.

Antisocial Personality Disorder (ASPD) & Psychopathy

ASPD requires conduct disorder before age 15 plus adult pattern of disregard for/violation of others’ rights. Psychopathy (Hare’s PCL-R) adds affective features: shallow affect, callousness, lack of remorse, grandiosity.

The Psychopathy Checklist–Revised (PCL-R) is a 20-item clinician-rated instrument that assesses psychopathic traits across two factors:

A score ≥30 (out of 40) is the conventional research threshold for psychopathy. Only a subset of individuals with ASPD meet psychopathy criteria — ASPD emphasises behavioural history, while psychopathy emphasises affective/interpersonal traits.

Neuroimaging findings in ASPD/psychopathy consistently show reduced amygdala volume and reactivity (impaired fear conditioning and empathic responding) and structural/functional deficits in the prefrontal cortex (particularly ventromedial PFC and orbitofrontal cortex), which are critical for moral reasoning, impulse control, and decision-making. These neural deficits help explain the characteristic disregard for consequences and lack of empathic concern.

Prevalence: ASPD ~3% men, 1% women. Heritability moderate; environmental factors (abuse, poverty, exposure to violence) contribute substantially. Notoriously difficult to treat; no established evidence-based therapy. Some evidence suggests that therapeutic community approaches and programmes targeting specific criminogenic needs can reduce recidivism, but core psychopathic traits appear resistant to change.

Other Notable PDs

• Schizotypal PD: odd beliefs, magical thinking, perceptual distortions; on schizophrenia spectrum genetically. Low-dose antipsychotics may help cognitive/perceptual symptoms.
• Narcissistic PD: grandiosity, need for admiration, lack of empathy; distinguished from healthy self-esteem by fragility. Two subtypes are recognised clinically: grandiose (overt entitlement, exploitativeness) and vulnerable (hypersensitivity, shame-proneness, social withdrawal).
• Avoidant PD: social inhibition, feelings of inadequacy, hypersensitivity to criticism; overlaps substantially with generalized SAD. The distinction is debated — some researchers argue they are the same condition varying in severity.
• Dependent PD: excessive need to be taken care of, leading to submissive and clinging behaviour, difficulty making independent decisions, and fear of separation. Distinguished from normal attachment by pervasiveness and the inability to function autonomously.
• Obsessive-Compulsive Personality Disorder (OCPD): preoccupation with orderliness, perfectionism, and control — at the expense of flexibility, openness, and efficiency. Despite its name, OCPD is distinct from OCD: OCPD traits are ego-syntonic (the person views their perfectionism as desirable), whereas OCD obsessions are ego-dystonic. OCPD is the most prevalent personality disorder (~2–8% in the general population). Comorbidity between OCD and OCPD is only moderate (~25%), and their neurobiological profiles differ.

Alternative DSM-5 Model

The DSM-5 Section III proposes a dimensional–categorical hybrid model that fundamentally reconceptualises personality pathology. It has two main components:

Criterion A — Level of Personality Functioning: rated on a 5-point scale (0 = healthy, 4 = extreme impairment) across two domains — self (identity, self-direction) and interpersonal (empathy, intimacy). A rating ≥2 is required for diagnosis. This addresses the core feature of personality disorders: disrupted sense of self and impaired relationship patterns.

Criterion B — Pathological Personality Traits: five broad trait domains (resembling a maladaptive version of the Big Five/OCEAN model):

The alternative model retains six specific PD types (antisocial, avoidant, borderline, narcissistic, obsessive-compulsive, schizotypal) — each defined by a specific constellation of impaired functioning and trait elevations — plus a Personality Disorder—Trait Specified option for presentations that do not fit a named type. This model represents the field’s direction of travel and is likely to be more prominent in future editions of the DSM.

Chapter 11: Substance-Related and Addictive Disorders

Definitions and Classification

The 11 criteria are organised into four groupings:

Importantly, tolerance and withdrawal alone do not constitute SUD — they can occur with prescribed medications taken as directed (e.g., opioids for chronic pain). The DSM-5 explicitly excludes tolerance/withdrawal during appropriate medical treatment from the diagnostic count.

Substance Classes and Mechanisms

Detailed Mechanisms by Class

Alcohol enhances inhibitory GABA transmission and suppresses excitatory glutamate (NMDA receptor antagonism), producing sedation, anxiolysis, and disinhibition. Chronic use leads to neuroadaptive upregulation of glutamate receptors and downregulation of GABA receptors — when alcohol is withdrawn, the resulting excitatory/inhibitory imbalance produces dangerous hyperexcitability (seizures, delirium tremens).

Cocaine blocks the dopamine transporter (DAT), preventing reuptake and flooding the synapse with dopamine. The intense but short-lived euphoria (“rush”) from smoked crack cocaine (onset: seconds) contributes to extremely rapid reinforcement and compulsive use patterns. Methamphetamine not only blocks DAT but also reverses the transporter, actively pumping dopamine into the synapse and triggering release from vesicles — producing a longer, more intense high than cocaine. Methamphetamine is highly neurotoxic, damaging dopaminergic and serotonergic neurons; chronic users show cognitive deficits and structural brain changes (reduced grey matter in frontal and temporal cortex).

Opioids bind to μ (mu) opioid receptors in the brain, spinal cord, and gastrointestinal tract. Activation of mu receptors in the VTA releases dopamine in the nucleus accumbens (reward), while activation in the periaqueductal grey and spinal cord produces powerful analgesia. The opioid epidemic has been driven largely by prescription opioid overprescription, followed by transition to heroin and illicit fentanyl (a synthetic opioid 50–100× more potent than morphine). Opioid overdose causes respiratory depression (mu receptors in the brainstem’s respiratory centres) and is reversed by naloxone, an opioid antagonist.

Caffeine use disorder is included in DSM-5 Section III as a condition requiring further study. Although caffeine is the world’s most widely used psychoactive substance, only a minority of users develop a problematic pattern characterised by persistent desire or unsuccessful efforts to cut down, continued use despite knowledge of physical or psychological harm, and withdrawal symptoms (headache, fatigue, irritability, difficulty concentrating).

Neurobiological Model of Addiction

The mesolimbic dopamine pathway — projecting from the ventral tegmental area (VTA) to the nucleus accumbens (NAc) — is the core neural substrate of reward and reinforcement. All drugs of abuse, despite their diverse pharmacological mechanisms, converge on this pathway by increasing dopamine release in the NAc. The VTA also projects to the prefrontal cortex (PFC) via the mesocortical pathway, which is involved in decision-making, impulse control, and assigning value to actions. Chronic substance use impairs PFC function, contributing to compulsive drug-seeking despite negative consequences.

Dopamine surge during acute use → neuroadaptation → tolerance. Incentive salience theory (Berridge & Robinson): wanting (dopaminergic, driven by cue-conditioned incentive salience) dissociates from liking (hedonic pleasure, mediated by opioid and endocannabinoid systems in the NAc); cue-triggered wanting persists even after liking diminishes, explaining why addicted individuals crave drugs intensely even when the drug no longer produces much pleasure. Allostatic model (Koob): chronic use shifts the hedonic set point downward; the brain’s anti-reward system (CRF, dynorphin, norepinephrine) becomes hyperactive during withdrawal, producing dysphoria and negative affect. Negative reinforcement (relief from this withdrawal-related distress) increasingly drives continued use as addiction progresses.

Alcohol Use Disorder (AUD)

Most prevalent SUD globally — approximately 14.5 million adults in the U.S. alone meet criteria for AUD. In Canada, alcohol causes more hospitalisations than heart attacks. AUD is highly comorbid with depression, anxiety, and PTSD; approximately 37% of individuals with AUD have a co-occurring mood disorder.

Acute alcohol withdrawal can be life-threatening. The withdrawal syndrome follows a predictable timeline: 6–12 hours (tremor, anxiety, nausea, insomnia), 12–24 hours (possible hallucinations), 24–48 hours (risk of withdrawal seizures), 48–72 hours (risk of delirium tremens — confusion, autonomic instability, hallucinations, agitation; mortality 5–15% if untreated). Chronic heavy use → Wernicke–Korsakoff syndrome: Wernicke’s encephalopathy (acute: confusion, ataxia, ophthalmoplegia; caused by thiamine/vitamin B1 deficiency) may progress to Korsakoff syndrome (chronic: severe anterograde amnesia, confabulation). Thiamine replacement is essential and urgent.

Treatment Approaches for Substance Use Disorders

Treatment typically involves multiple stages and modalities.

Detoxification (detox) is the medically supervised management of acute withdrawal. For alcohol, benzodiazepines (e.g., chlordiazepoxide, lorazepam) are used to prevent seizures and delirium tremens. For opioids, medically assisted withdrawal uses tapering doses of methadone or buprenorphine to ease symptoms.

Pharmacotherapy uses three main strategies:

Acamprosate normalises the glutamate/GABA imbalance caused by chronic alcohol use, reducing protracted withdrawal symptoms and craving. It is most effective for maintaining abstinence after detox.

Psychosocial treatments:

Motivational Interviewing (MI) addresses ambivalence about change using a non-confrontational, empathic approach. The four core principles are captured by the acronym OARS: Open-ended questions, Affirmations, Reflective listening, and Summarising. MI helps patients move through stages of change (precontemplation → contemplation → preparation → action → maintenance) by eliciting and strengthening the patient’s own motivation for change rather than imposing it externally.

Contingency management (CM) provides tangible reinforcement (e.g., vouchers, prize draws) for verified drug-free urine samples. CM has among the largest effect sizes of any addiction treatment, particularly for stimulant use disorders where no approved pharmacotherapy exists. Despite its efficacy, CM is underused due to concerns about cost and the ethics of “paying” patients.

Cognitive-behavioural relapse prevention (Marlatt & Gordon) teaches patients to identify high-risk situations, develop coping strategies, and manage lapses without full relapse. The model distinguishes between a lapse (a single instance of substance use) and a relapse (a return to pre-treatment patterns of use). The abstinence violation effect (AVE) occurs when a lapse triggers catastrophic thinking (“I’ve failed — I might as well keep using”), which turns a lapse into a full relapse. Relapse prevention therapy teaches patients to: (1) identify personal high-risk situations (emotional states, social pressures, environmental cues); (2) develop specific coping responses for each; (3) reframe lapses as learning opportunities rather than failures; and (4) practise lifestyle balance to reduce overall vulnerability.

Twelve-step facilitation and mutual support groups (e.g., Alcoholics Anonymous, Narcotics Anonymous) provide peer support, accountability, and a structured recovery framework. AA’s abstinence-oriented approach is not suitable for all individuals, but large-scale studies (including the Cochrane-reviewed Project MATCH) show that AA/twelve-step facilitation produces abstinence outcomes at least as good as CBT and motivational enhancement therapy.

Residential treatment (rehabilitation centres) provides structured, drug-free environments for intensive treatment, typically lasting 28–90 days. Therapeutic communities offer longer-term (6–12 month) immersive environments emphasising personal accountability and peer-driven recovery. These settings are most appropriate for individuals with severe SUDs, limited social support, or co-occurring disorders.

Gambling Disorder

Only behavioural addiction in DSM-5. Shares neurobiological features with substance use (reward circuitry dysregulation — blunted striatal dopamine response, impaired PFC-mediated decision making). Criteria mirror SUD: preoccupation, tolerance (needing to gamble with more money), withdrawal-like irritability, failed attempts to cut down, chasing losses, lying about extent of gambling, jeopardizing relationships/career, relying on others for money. Prevalence ~0.4–1% of adults; higher among males, younger adults, and individuals with comorbid substance use.

Chapter 12: Schizophrenia Spectrum Disorders

Schizophrenia

Prevalence ~1% worldwide, similar across cultures. Onset typically late adolescence/early adulthood; earlier in males (18–25) than females (25–35). The sex difference in onset may partly reflect the neuroprotective effects of oestrogen, and female-onset schizophrenia shows a second incidence peak around menopause (when oestrogen declines). The course of schizophrenia is variable: approximately 20–25% experience a single episode with good recovery, ~50% have a relapsing-remitting course, and ~25% have a chronic, deteriorating course. Contrary to earlier pessimistic views, long-term outcome studies show that many individuals with schizophrenia experience substantial improvement over decades, particularly with early intervention and sustained treatment.

Prodromal Phase and At-Risk Mental States

Schizophrenia rarely emerges abruptly. Most individuals experience a prodromal phase lasting months to years before full psychosis, characterised by social withdrawal, declining academic/occupational performance, unusual perceptual experiences, suspiciousness, and disorganised thinking. The concept of At-Risk Mental State (ARMS) or Clinical High Risk for Psychosis (CHR-P) identifies individuals showing attenuated psychotic symptoms (e.g., fleeting hallucinations, overvalued ideas that are not yet fixed delusions) or brief intermittent psychotic episodes. Approximately 20–35% of CHR-P individuals convert to full psychotic disorder within 2–3 years. Early detection and intervention during the ARMS phase — including CBT, family support, and low-dose antipsychotics when indicated — can delay or prevent transition to psychosis.

Positive symptoms (excess/distortion of normal function):

• Delusions: fixed false beliefs (persecutory, referential, grandiose, somatic)
• Hallucinations: most commonly auditory (voices commenting, conversing)
• Disorganized thinking: loose associations, tangentiality, word salad
• Catatonia: motoric unresponsiveness or excitement

Negative symptoms (diminution of normal function): avolition, alogia, anhedonia, affective flattening, asociality. More treatment-resistant and predictive of functional outcome.

Cognitive deficits are now recognised as a core feature of schizophrenia, present before psychosis onset and persisting even when positive symptoms remit. Key impairments include working memory (difficulty holding and manipulating information), processing speed (slower performance on timed tasks), attention/vigilance, and verbal learning and memory. Cognitive deficits are the strongest predictor of real-world functional outcomes (employment, independent living, social relationships) — more so than positive or negative symptoms.

Social cognition deficits are particularly debilitating. Individuals with schizophrenia show impairments in emotion recognition (difficulty identifying facial expressions), theory of mind (difficulty inferring others’ mental states), and attributional style (tendency toward hostile attribution biases). These deficits contribute to social isolation and interpersonal difficulties. Social cognitive training programmes are an emerging treatment target.

Neurobiology

Dopamine hypothesis: the original version (Carlsson, 1960s) proposed a simple excess of dopamine. The revised dopamine hypothesis specifies regional imbalances: positive symptoms result from hyperdopaminergia in the mesolimbic pathway (excess dopamine in the striatum, particularly the associative striatum); negative and cognitive symptoms from hypodopaminergia in the mesocortical pathway (PFC dopamine deficit). Evidence supporting this hypothesis includes: (1) all effective antipsychotics block D2 receptors; (2) dopamine agonists (amphetamine, L-DOPA) can induce psychotic symptoms; (3) PET studies show elevated presynaptic dopamine synthesis capacity in the striatum of patients with schizophrenia.

Glutamate hypothesis: NMDA receptor hypofunction explains the broader symptom profile more comprehensively than the dopamine hypothesis alone. Evidence comes from the observation that ketamine and PCP (NMDA antagonists) produce positive, negative, and cognitive symptoms in healthy individuals — unlike dopamine agonists, which primarily produce positive symptoms. The glutamate hypothesis has led to investigation of glycine-site NMDA receptor modulators as potential novel treatments.

Structural: enlarged ventricles, reduced grey matter in PFC, temporal lobes, and hippocampus. Progressive grey matter loss occurs in the early years of illness. Heritability \(h^2 \approx 0.79{-}0.85\); monozygotic twin concordance ~48% (highlighting substantial environmental contribution despite high heritability).

Cannabis is now well-established as a risk factor for psychosis. A dose–response relationship exists: daily use of high-potency cannabis during adolescence increases the risk of developing schizophrenia approximately 5-fold. Cannabis likely interacts with genetic vulnerability (e.g., variation in the COMT gene) rather than causing psychosis de novo, consistent with a G×E interaction model.

Neurodevelopmental model: prenatal insults (infection, malnutrition, obstetric complications) + genetic vulnerability → aberrant neural circuitry → psychosis triggered by adolescent stress. This model explains the characteristic gap between neurodevelopmental disruption (prenatal/perinatal) and symptom onset (late adolescence) — the adolescent brain undergoes extensive synaptic pruning and myelination, and these normal maturational processes may unmask latent neural circuitry deficits.

Treatment

Typical (first-generation) antipsychotics (e.g., haloperidol, chlorpromazine) primarily block D2 receptors in the mesolimbic pathway, effectively treating positive symptoms. However, D2 blockade in other pathways causes significant side effects:

Tardive dyskinesia (TD) — involuntary, repetitive movements of the face, tongue, and limbs — develops in ~20–30% of patients on long-term typical antipsychotics and may be irreversible.

Atypical (second-generation) antipsychotics (e.g., clozapine, risperidone, olanzapine, quetiapine, aripiprazole): have a broader receptor profile (5-HT2A antagonism in addition to D2 antagonism); lower EPS risk; but many cause significant metabolic side effects (weight gain, dyslipidaemia, hyperglycaemia, increased risk of type 2 diabetes and cardiovascular disease), particularly olanzapine and clozapine. Clozapine is the most effective antipsychotic for treatment-resistant schizophrenia (defined as failure to respond to ≥2 adequate antipsychotic trials), producing response in ~30–60% of treatment-resistant patients. However, it requires regular blood monitoring due to the risk of agranulocytosis (potentially fatal drop in white blood cells; incidence ~1%).

Psychosocial: CBTp (CBT for psychosis), family therapy (reduce expressed emotion/EE), supported employment. High EE (hostility, critical comments, overinvolvement) in family → ↑ relapse rate.

Long-acting injectable antipsychotics (LAIs) (e.g., paliperidone palmitate, aripiprazole lauroxil) are administered every 2–12 weeks and address medication non-adherence — the single most common cause of relapse. LAIs ensure consistent medication levels and reduce relapse and rehospitalisation rates compared to oral medications.

Coordinated Specialty Care (CSC) is a team-based model for first-episode psychosis that integrates low-dose antipsychotics, individual CBTp, family education and support, supported education/employment, and case management. The landmark RAISE-ETP study demonstrated that CSC produces superior outcomes (symptoms, quality of life, employment) compared to treatment as usual, particularly when initiated early. CSC represents a paradigm shift toward intensive early intervention, recognising that the first 2–5 years after psychosis onset (the “critical period”) offer the greatest opportunity to alter the long-term trajectory of the illness.

Spectrum Disorders

The schizophrenia spectrum includes several related disorders that differ primarily in duration, symptom profile, and the presence of mood symptoms.

• Schizophreniform disorder: same criteria as schizophrenia, but total duration is 1–6 months. Approximately two-thirds of individuals diagnosed with schizophreniform disorder eventually meet criteria for schizophrenia; the remainder recover fully.
• Schizoaffective disorder: requires a period during which a major mood episode (depressive or manic) co-occurs with schizophrenia symptoms, plus ≥2 weeks of psychotic symptoms without prominent mood symptoms. This disorder occupies a conceptual middle ground between schizophrenia and bipolar disorder, and some researchers question whether it is a distinct entity or simply comorbid presentations.
• Delusional disorder: one or more non-bizarre delusions (situations that could conceivably occur in real life, e.g., being followed, poisoned, loved at a distance, or having a disease) for ≥1 month; no other psychotic features, and functioning is relatively preserved outside the delusional system. Subtypes: erotomanic, grandiose, jealous, persecutory, somatic, mixed.
• Brief psychotic disorder: 1 day–1 month, with full return to premorbid functioning; often precipitated by acute stress.
• Attenuated psychosis syndrome: included in DSM-5 Section III as a condition for further study; captures the ARMS/CHR-P concept described above.

Chapter 13: Sexual Dysfunctions, Gender Dysphoria, and Paraphilic Disorders

Sexual Dysfunctions

Biopsychosocial factors include: vascular disease, hormonal imbalance (testosterone deficiency, thyroid dysfunction), medications (SSRIs cause sexual dysfunction in 30–70% of users), anxiety/depression, relationship conflict, cultural shame, and history of sexual trauma.

Models of Sexual Response

The traditional Masters and Johnson (1966) linear model describes four phases: excitement → plateau → orgasm → resolution. Kaplan (1979) added a desire phase before arousal. However, these linear models poorly capture female sexual response.

Basson’s (2000) circular model of female sexual response proposes that many women do not begin a sexual encounter with spontaneous desire. Instead, the cycle may begin with sexual neutrality — the woman is receptive to sexual stimuli for reasons beyond desire (emotional closeness, relationship maintenance). If the context is sufficiently safe and stimulating, subjective arousal develops, which then generates responsive desire. The circular model highlights that desire and arousal are not always sequential — they may co-occur or arousal may precede desire. This model has important clinical implications: women who experience responsive rather than spontaneous desire are not dysfunctional.

The Dual Control Model (Bancroft & Janssen) proposes that sexual response is governed by the balance between sexual excitation (SE) and sexual inhibition (SI) systems. SI is further divided into SI1 (inhibition due to threat of performance failure) and SI2 (inhibition due to threat of negative consequences). Individual variation in SE/SI balance explains why some people are more vulnerable to sexual dysfunction (high SI) or sexual risk-taking (high SE, low SI). The model applies across genders and sexual orientations.

Sensate focus (Masters & Johnson) is the foundational psychological treatment for sexual dysfunctions. It involves a structured series of touching exercises designed to reduce performance anxiety by removing the goal of orgasm and refocusing attention on pleasurable sensations. PDE5 inhibitors (sildenafil, tadalafil, vardenafil) treat erectile disorder by inhibiting phosphodiesterase-5, an enzyme that breaks down cGMP — the molecule responsible for smooth muscle relaxation in penile blood vessels. By preserving cGMP levels, PDE5 inhibitors facilitate erection in the presence of sexual stimulation (they do not produce erection in the absence of arousal).

Consent Frameworks

Contemporary sexual health education increasingly emphasises affirmative consent — the principle that consent must be freely given, reversible, informed, enthusiastic, and specific (the “FRIES” model). Consent is an ongoing process, not a one-time event. From a clinical perspective, understanding consent is relevant because many sexual dysfunctions develop in contexts of coercion, trauma, or power imbalance. Clinicians must assess for these factors when evaluating sexual complaints.

Gender Dysphoria

Separate criteria for children vs. adolescents/adults. In children, ≥6 of 8 criteria are required, including a strong desire to be of the other gender, preference for cross-gender roles in play, and strong dislike of one’s own sexual anatomy.

Gender dysphoria is distinct from gender nonconformity, which is not a mental disorder. The DSM-5’s inclusion of gender dysphoria has been debated: some argue that any classification pathologises gender diversity, while others note that the diagnosis facilitates access to insurance-covered medical treatments.

Treatment follows a gender-affirming care model:

Each stage involves careful assessment, informed consent, and ideally a multidisciplinary team. Research consistently demonstrates that gender-affirming care significantly improves mental health outcomes: a large 2022 study showed that access to gender-affirming hormones was associated with 60% lower odds of moderate/severe depression and 73% lower odds of suicidality. High rates of comorbid depression and anxiety often reflect minority stress (discrimination, harassment, family rejection, social stigma) rather than inherent features of gender incongruence.

Paraphilic Disorders

A paraphilia is an atypical sexual interest; it becomes a paraphilic disorder only when it causes significant distress/impairment to the individual or involves harm to others (non-consenting persons or children).

Treatments: cognitive-behavioural relapse prevention, anti-androgen pharmacotherapy for high-risk offenders.

Chapter 14: Neurodevelopmental Disorders (ADHD & ASD)

Attention-Deficit/Hyperactivity Disorder (ADHD)

Three presentations:

• Primarily inattentive: difficulty sustaining attention, easily distracted, forgetful, loses things, fails to follow through on tasks, avoids tasks requiring sustained mental effort
• Primarily hyperactive–impulsive: fidgets, leaves seat, runs/climbs inappropriately, talks excessively, blurts out answers, difficulty waiting turn, interrupts others
• Combined: meets criteria for both inattentive and hyperactive–impulsive presentations

Prevalence ~7% in children, ~4% in adults (though adult ADHD is increasingly recognised as underdiagnosed). Male-to-female ratio ~3:1 in clinical samples (but closer to 1.6:1 in epidemiological studies — see female presentation below). Heritability \(h^2 \approx 0.76\) — one of the most heritable psychiatric conditions. Candidate genes include DRD4 (dopamine D4 receptor), DAT1/SLC6A3 (dopamine transporter), and DRD5, though GWAS have identified over 12 genome-wide significant loci, each of small effect.

Barkley’s executive function model: core deficit is in behavioural inhibition, impairing self-regulation across time. Prefrontal cortex and striatum are structurally/functionally atypical; delayed cortical maturation (on average ~3 years delayed peak cortical thickness).

Executive Function Deficits in ADHD

In ADHD, deficits in executive function manifest as difficulty sustaining attention to tedious tasks, poor time management, disorganisation, difficulty shifting between tasks, and problems holding information in mind while using it. These deficits are not due to a lack of intelligence or motivation — individuals with ADHD often perform well on tasks that are intrinsically interesting or immediately rewarding, reflecting a motivational/reward-processing component in addition to cognitive control deficits.

Female Presentation of ADHD

ADHD in girls and women is systematically underdiagnosed. The 3:1 male-to-female ratio in clinical samples narrows to approximately 1.6:1 in epidemiological (community) samples, suggesting that many females with ADHD are not being identified. This underdiagnosis occurs because females more often present with the primarily inattentive subtype (daydreaming, disorganisation, difficulty completing tasks) rather than the hyperactive-impulsive presentation that is more disruptive and more likely to prompt referral. Girls with ADHD are more likely to develop compensatory strategies, internalise their difficulties as personal failures, and present with comorbid anxiety and depression rather than the externalising behaviours (aggression, defiance) more typical in boys. Diagnosis is often delayed until adolescence or adulthood, when academic demands exceed compensatory capacity.

Treatment: stimulant medications (methylphenidate, amphetamine salts) are highly effective — they increase dopamine/NE in PFC via DAT/NET blockade. Non-stimulants: atomoxetine (NET inhibitor), guanfacine (alpha-2A agonist). Psychosocial: parent management training, school accommodations, organizational skills training. For adults, CBT targeting time management, organisation, and emotional regulation is increasingly supported by evidence.

Autism Spectrum Disorder (ASD)

Prevalence has risen substantially over recent decades — from ~1 in 150 (2000) to ~1 in 36 (US CDC 2023). This increase likely reflects broadened diagnostic criteria, increased awareness, better surveillance, and diagnostic substitution (children previously diagnosed with intellectual disability or language disorders now receiving ASD diagnoses) rather than a true epidemic. Male-to-female ratio ~4:1; females often present with more camouflaging, leading to underdiagnosis (see below).

DSM-5 collapsed previous subtypes (Autistic Disorder, Asperger’s Disorder, PDD-NOS) into a single spectrum with three severity levels:

Social–communication deficits: reduced reciprocity, abnormal eye contact/nonverbal communication, difficulty developing/maintaining relationships.

Theory of Mind in ASD

Theory of mind deficits are a hallmark of ASD. The classic Sally-Anne false belief task demonstrates that young children with ASD have difficulty understanding that another person can hold a belief that differs from reality. While many individuals with ASD develop explicit ToM abilities over time (they can pass laboratory tasks), implicit, spontaneous mentalizing in real-time social interaction often remains impaired. This contributes to difficulties with conversational turn-taking, understanding sarcasm and irony, predicting others’ behaviour, and navigating complex social situations.

Restricted/repetitive behaviours (RRBs): stereotypies (e.g., hand flapping, rocking), insistence on sameness, highly restricted fixated interests, and hyper/hyposensitivity to sensory input.

Sensory Processing in ASD

Approximately 90% of individuals with ASD exhibit atypical sensory processing. This can manifest as hypersensitivity (e.g., distress from loud sounds, certain textures, bright lights, or food textures), hyposensitivity (e.g., reduced pain perception, seeking intense sensory input such as spinning or deep pressure), or both across different modalities. Sensory differences are now recognised as a core diagnostic feature in DSM-5 (included under the RRB domain) and can significantly impact daily functioning, dietary habits, tolerance of environments, and social participation.

Heritability \(h^2 > 0.80\); hundreds of risk genes identified — no single “autism gene.” Extreme male brain theory (Baron-Cohen): systemizing > empathizing cognitive style. Gut–brain axis and immune dysregulation hypotheses under active research. Prenatal factors (advanced paternal age, valproate exposure) increase risk.

Female Presentation of ASD (Masking and Camouflaging)

Similar to ADHD, ASD is underdiagnosed in females (the 4:1 male-to-female ratio may partly reflect diagnostic bias). Girls and women with ASD are more likely to engage in camouflaging (also called masking) — consciously or unconsciously compensating for social difficulties by imitating neurotypical social behaviours, rehearsing scripts for conversations, forcing eye contact, and suppressing stimming in public. While camouflaging may facilitate social inclusion in the short term, it is cognitively exhausting and associated with increased rates of anxiety, depression, burnout, and suicidality. Many women receive an ASD diagnosis only in adulthood, after years of being misdiagnosed with anxiety, depression, BPD, or eating disorders.

Treatment: Applied Behaviour Analysis (ABA) has the most evidence for skill acquisition, particularly in early intensive behavioural intervention (EIBI) programmes. However, ABA is increasingly controversial. Critics — including many autistic self-advocates — argue that traditional ABA focuses on eliminating autistic behaviours to achieve neurotypical conformity rather than supporting the individual’s wellbeing. Concerns include the suppression of stimming (which may serve important self-regulatory functions), high treatment intensity (historically 20–40 hours/week), and potential psychological harm from compliance-based approaches. Contemporary ABA has evolved considerably, with many practitioners adopting naturalistic, play-based, and child-led approaches that prioritise functional skills and quality of life.

The neurodiversity movement offers an alternative framework, viewing autism as a natural variation in human neurology rather than a disorder requiring correction. Neurodiversity advocates argue for accommodations and acceptance rather than normalisation. This perspective does not deny that autistic individuals may need support — particularly for co-occurring conditions like anxiety, sensory overwhelm, or communication challenges — but reframes the goal from “fixing” autism to enabling autistic people to thrive as they are. The tension between the medical model and the neurodiversity paradigm is one of the most important ongoing debates in the field.

Speech-language therapy, occupational therapy (especially for sensory integration), and social skills training remain important supports. No pharmacological treatment exists for core ASD; medications target comorbidities (anxiety: SSRIs; ADHD: stimulants; irritability: risperidone, aripiprazole).

Other Neurodevelopmental Disorders

• Intellectual Developmental Disorder (IDD): deficits in intellectual (\(IQ < 70\)) and adaptive functioning (conceptual, social, practical domains), with onset in the developmental period. Severity is determined primarily by adaptive functioning: mild (~85% of IDD; can live semi-independently), moderate, severe, and profound. Causes include genetic syndromes (Down syndrome/trisomy 21, Fragile X), prenatal exposures (fetal alcohol spectrum disorder), perinatal complications, and environmental deprivation.
• Specific Learning Disorder: affects ~5–15% of school-age children. Subtypes: dyslexia (difficulty with accurate/fluent word reading and spelling), dysgraphia (difficulty with written expression), dyscalculia (difficulty with number sense, arithmetic, mathematical reasoning). SLD is not explained by intellectual disability, sensory deficits, or inadequate instruction. Individuals with SLD often require accommodations (extended time, assistive technology) and specialised instruction (e.g., Orton-Gillingham for dyslexia).
• Developmental Coordination Disorder (DCD): impaired acquisition and execution of coordinated motor skills; affects ~5–6% of children. Manifests as clumsiness, slow/inaccurate motor performance, and difficulty with daily motor tasks (handwriting, using utensils, sports).
• Communication Disorders: language disorder, speech sound disorder, childhood-onset fluency disorder (stuttering), social (pragmatic) communication disorder (difficulty with social use of language — turn-taking, adjusting speech to context, understanding inference — without restricted/repetitive behaviours; this diagnosis is mutually exclusive with ASD).
• Tic Disorders / Tourette’s: motor and/or vocal tics; Tourette’s disorder = ≥2 motor + ≥1 vocal tic, present for ≥1 year, onset before age 18. Tics are semi-voluntary — individuals often experience a premonitory urge and temporary ability to suppress tics, but suppression is effortful and increases subsequent tic frequency. Prevalence ~0.3–0.8%. Commonly comorbid with ADHD and OCD. Treatment: habit reversal training (HRT), Comprehensive Behavioural Intervention for Tics (CBIT), and in severe cases, alpha-2 agonists (clonidine, guanfacine) or antipsychotics (aripiprazole).

Chapter 15: Neurocognitive Disorders

Overview

Major NCD (Dementia): significant cognitive decline impairing independence in daily activities. Mild NCD (Mild Cognitive Impairment, MCI): modest decline; independence preserved with compensatory strategies. Delirium: acute, fluctuating disturbance of attention and awareness with cognitive deficits; not a chronic condition.

Delirium

Rapid onset (hours–days), fluctuating course, disturbance in attention and awareness, additional cognitive disturbance. Causes include medical illness (infection, metabolic disturbance, organ failure), medications (anticholinergics, opioids, benzodiazepines), substance intoxication/withdrawal, and post-surgical states. Delirium is especially common in hospitalized elderly (affecting 15–50% of older inpatients) and is associated with increased mortality, prolonged hospitalization, and accelerated cognitive decline.

Management priorities: identify and treat the underlying cause (the delirium itself is a symptom, not a primary disorder); provide environmental reorientation (clocks, calendars, familiar objects, consistent caregivers, adequate lighting); ensure adequate hydration and nutrition; minimise use of deliriogenic medications; reserve low-dose antipsychotics (haloperidol) for severe agitation with risk of harm. Prevention is the most effective strategy — the Hospital Elder Life Program (HELP) reduces delirium incidence by ~30% through systematic attention to risk factors (cognitive stimulation, sleep hygiene, mobility, vision/hearing optimisation, hydration).

Alzheimer’s Disease (AD)

Most common dementia (~60–80% of cases). Pathology: amyloid-β plaques and neurofibrillary tau tangles → neuronal death, beginning in the entorhinal cortex/hippocampus → progressive cortical spread.

Clinical course progresses through recognisable stages:

Mean survival is 8–10 years after diagnosis, though this varies considerably. Behavioural and psychological symptoms of dementia (BPSD) — including agitation, aggression, psychosis (delusions, hallucinations), depression, apathy, and sleep disturbance — affect up to 90% of patients at some point and are the primary driver of caregiver distress and institutionalisation.

Risk factors: age (prevalence doubles every 5 years after age 65), APOE-ε4 allele (one copy ↑ risk ~3×; two copies ↑ risk ~8–12×), family history, TBI, cardiovascular risk factors (what is bad for the heart is bad for the brain), lower educational attainment (less cognitive reserve).

Cholinergic hypothesis: loss of ACh-producing neurons in the nucleus basalis of Meynert (projecting to cortex) underlies memory and attention deficits. Treatments: acetylcholinesterase inhibitors (donepezil, rivastigmine, galantamine) and memantine (NMDA antagonist) — modest symptomatic benefit, not disease-modifying. Novel disease-modifying agents targeting the amyloid cascade have received regulatory approval: lecanemab (2023) and donanemab (2024) are anti-amyloid monoclonal antibodies that reduce brain amyloid plaque burden and slow cognitive decline by approximately 25–35% over 18 months. However, they carry risks of amyloid-related imaging abnormalities (ARIA) — brain oedema and microhaemorrhages — particularly in APOE-ε4 homozygotes, and their clinical meaningfulness is debated.

Other Major NCDs

Vascular NCD

Vascular NCD results from cerebrovascular disease — either ischemic stroke (blockage of blood supply to brain tissue) or hemorrhagic stroke (rupture of a blood vessel in the brain). The cognitive profile depends on lesion location and extent. Multi-infarct dementia presents with a characteristic stepwise decline — abrupt worsening after each stroke event, with periods of stability between. Small vessel disease produces a more gradual decline, predominantly affecting executive function (planning, set-shifting, working memory) and processing speed, often with relatively preserved episodic memory early in the course. Focal neurological signs (hemiparesis, visual field cuts, gait disturbance) are common. Risk factors mirror those for cardiovascular disease: hypertension, diabetes, hyperlipidaemia, smoking, and atrial fibrillation. Prevention through vascular risk factor management is the most effective intervention.

Lewy Body NCD

Lewy body NCD (also called dementia with Lewy bodies, DLB) is the second most common neurodegenerative dementia after AD. It is caused by abnormal deposits of alpha-synuclein (Lewy bodies) in cortical and subcortical neurons. The four core clinical features form a distinctive presentation:

A critical clinical consideration is that patients with DLB are exquisitely sensitive to antipsychotic medications — even low doses can trigger severe parkinsonism, neuroleptic malignant syndrome, or rapid cognitive decline. Cholinesterase inhibitors (rivastigmine) may improve cognitive and neuropsychiatric symptoms.

Frontotemporal NCD (FTD)

Frontotemporal NCD encompasses a group of disorders characterised by progressive degeneration of the frontal and/or temporal lobes. Typical onset is in the 50s–60s, making it the most common cause of dementia in individuals under 60. There are two major clinical variants:

• Behavioural variant FTD (bvFTD): progressive personality change, disinhibition (socially inappropriate behaviour, impulsivity), apathy, loss of empathy, compulsive/ritualistic behaviours, hyperorality (dietary changes, binge eating), and executive dysfunction — often initially misdiagnosed as a psychiatric disorder (depression, mania, or personality change).
• Language variants (Primary Progressive Aphasias): semantic variant (loss of word meaning, with fluent but empty speech) and nonfluent/agrammatic variant (effortful, halting speech with grammatical errors). A third variant, logopenic PPA, is more often associated with AD pathology.

FTD pathology involves accumulation of tau or TDP-43 protein inclusions. There is no effective pharmacological treatment; management focuses on behavioural strategies and caregiver support.

Other Aetiologies

Neuropsychological Assessment and Biomarkers

Screening: MMSE (max 30; <24 suggests impairment) and MoCA (more sensitive to MCI; includes executive function tasks like Trail Making and clock drawing). Comprehensive neuropsychological battery assesses all six cognitive domains systematically, establishing a cognitive profile that aids differential diagnosis.

Biomarkers are transforming early detection and diagnosis of neurocognitive disorders:

The development of accessible blood-based biomarkers like plasma p-tau217 represents a paradigm shift — enabling population-level screening and earlier intervention that was previously impractical.

Caregiving and Ethics

Dementia places enormous burden on caregivers: depression (affecting 30–40% of dementia caregivers), anxiety, social isolation, physical health deterioration, and financial strain. Caregiver burnout is a major concern, particularly for spousal caregivers and those caring for individuals with behavioural symptoms (aggression, wandering, sleep disturbance). Women bear a disproportionate share of caregiving responsibilities. Protective factors include social support, respite services, psychoeducation, and caregiver support groups. CBT-based interventions for caregivers have demonstrated efficacy in reducing depression and burden.

Ethical issues are pervasive in dementia care: decision-making capacity (which fluctuates and must be assessed in context-specific ways — a person may lack capacity for financial decisions while retaining capacity for simpler choices), advance directives (which must be established early while the individual can still express preferences), use of physical and chemical restraints (raising autonomy vs. safety tensions), truth-telling about diagnosis, and end-of-life care (including the ethics of assisted dying in jurisdictions where it is legal).

Chapter 16: Transdiagnostic Approaches

The Problem of Comorbidity

Throughout these notes, a striking pattern has recurred: disorders rarely travel alone. The National Comorbidity Survey Replication (Kessler et al., 2005) found that among individuals with any 12-month DSM disorder, approximately 45% met criteria for two or more disorders. The WHO World Mental Health Surveys confirmed similar rates cross-nationally — roughly 50% of people with one mental disorder have at least one additional diagnosis across their lifetime. Anxiety and depressive disorders co-occur at rates of 40–70% (Brown et al., 2001). Substance use disorders co-occur with other mental disorders approximately 50% of the time. Borderline personality disorder shows comorbidity rates exceeding 80% with Axis I disorders.

This extraordinary degree of diagnostic overlap demands explanation. Three accounts have been proposed:

The artifactual explanation suggests that comorbidity partly reflects overlapping diagnostic criteria — concentration difficulties appear in both MDD and GAD, psychomotor agitation in both mania and PTSD. When different categories share symptom criteria, co-diagnosis is baked into the system. The shared aetiology explanation proposes that disorders co-occur because they share underlying causal processes — genetic risk factors, neuroticism/negative affectivity, early adversity — rather than being truly distinct entities. The dimensional explanation argues that comorbidity rates are best understood if disorders represent arbitrary thresholds imposed on continuous dimensions of psychopathology, rather than natural categories: if depression and anxiety are really different regions on a shared spectrum, then “comorbidity” is simply what it looks like when a person falls in the overlap zone.

Barlow’s Triple Vulnerabilities Model

David Barlow’s triple vulnerabilities model (2000, 2002) provides an integrative framework for understanding why emotional disorders develop and why they overlap. The model proposes three layers of vulnerability:

Generalized biological vulnerability: A heritable contribution to negative affect and neuroticism. Behavioural genetics studies estimate that neuroticism is approximately 40–60% heritable (Hettema, Neale, & Kendler, 2001), with the risk being polygenic — many genes of small effect contributing to a temperamental tendency toward negative emotionality. Crucially, this vulnerability is nonspecific: it predisposes to emotional disorders generally, not to any particular disorder.

Generalized psychological vulnerability: Early developmental experiences that produce a diminished sense of personal control over events and emotional responses. Drawing on learned helplessness research (Seligman) and the perceived control literature, Barlow and Chorpita (1998) argued that parenting styles characterised by overcontrol, overprotection, and unpredictability foster a cognitive schema that the world is dangerous and uncontrollable. This vulnerability, like the biological one, is nonspecific — it increases risk for emotional disorders broadly by generating an anxious apprehension about the future.

Specific psychological vulnerability: Learning experiences that focus anxiety on particular objects, situations, or internal experiences. Through direct conditioning, observational learning, or informational transmission (Rachman, 1977), anxiety becomes associated with specific stimuli. This third vulnerability determines the form the disorder takes: if anxiety is focused on social evaluation → social anxiety disorder; on bodily sensations → panic disorder; on contamination → OCD; on health → illness anxiety disorder.

Because two of three vulnerabilities are shared across all emotional disorders, comorbidity is the expected outcome, not an anomaly. The Unified Protocol (described below) targets the first two — shared — vulnerabilities.

Shared Transdiagnostic Processes

Research has identified several psychological processes that operate across diagnostic boundaries and may better explain the structure of psychopathology than diagnostic categories.

Emotion Dysregulation

Difficulties in the awareness, understanding, acceptance, and strategic modulation of emotional responses are elevated across virtually every disorder covered in these notes. A landmark meta-analysis by Aldao, Nolen-Hoeksema, and Schweizer (2010) — spanning 114 studies — found that the relationship between emotion dysregulation strategies and psychopathology was not diagnosis-specific: the same maladaptive strategies (rumination, avoidance, suppression) predicted severity across anxiety, depression, eating disorders, and substance use, with medium-to-large effect sizes. In Linehan’s (1993) biosocial theory of BPD, emotion dysregulation is the core feature: biological emotional vulnerability interacts with an invalidating environment to produce pervasive difficulties in modulating emotional responses. Binge eating has been conceptualised as an emotion regulation strategy, and substance use is often understood through the lens of the self-medication hypothesis (Khantzian, 1997).

Cognitive Biases

Three families of cognitive bias operate transdiagnostically. Attentional bias to threat, demonstrated through dot-probe and emotional Stroop paradigms, is robust across all anxiety disorders (Bar-Haim et al., 2007 meta-analysis; d = 0.45) and is also present in depression, PTSD, eating disorders (bias toward body/food stimuli), and addiction (bias toward substance cues). Interpretation bias — the tendency to interpret ambiguous information negatively — has been documented across GAD, social anxiety, depression, and health anxiety (Mathews & MacLeod, 2005). Memory bias — preferential recall of negative information — is most consistently found in depression (mood-congruent memory) and PTSD, while overgeneral autobiographical memory (difficulty recalling specific positive memories) characterises depression, PTSD, and BPD.

Rumination and Repetitive Negative Thinking

Ehring and Watkins (2008) proposed that repetitive negative thinking (RNT) is a transdiagnostic process with shared features across disorders: it is repetitive, passive, abstract, and focused on negative content. The specific forms vary — depressive rumination, worry (GAD), post-event processing (social anxiety), intrusive rumination (PTSD), body-related rumination (eating disorders) — but the underlying process is common. Nolen-Hoeksema and Watkins (2011) marshalled longitudinal evidence showing that rumination precedes and predicts the onset of depression, anxiety, binge eating, and alcohol abuse, establishing it as a transdiagnostic risk factor rather than merely a symptom.

Avoidance

Behavioural avoidance — avoiding situations that trigger distress — is the central maintaining factor in all exposure-based models of anxiety, but it is equally present in depression (behavioural withdrawal), PTSD (the avoidance symptom cluster), and eating disorders (avoidance of feared foods and situations). Experiential avoidance — the unwillingness to remain in contact with aversive internal experiences (thoughts, feelings, sensations) and the effort to alter or escape them — is a core concept in Acceptance and Commitment Therapy (ACT). Chawla and Ostafin (2007) reviewed evidence that experiential avoidance is elevated across anxiety, depression, BPD, substance use, chronic pain, and psychosis. In every case, avoidance provides short-term distress reduction that negatively reinforces the pattern, preventing new learning and maintaining the disorder.

Intolerance of Uncertainty

Originally studied as a core cognitive vulnerability in GAD (Dugas et al., 1998), intolerance of uncertainty (IU) — the tendency to react negatively to uncertain situations regardless of their probability — is now recognised as transdiagnostic. It predicts obsessive symptoms in OCD (Holaway, Heimberg, & Coles, 2006), health anxiety severity (Boelen & Reijntjes, 2009), eating pathology (particularly in anorexia nervosa), and social anxiety. McEvoy and Mahoney (2012) found equivalently elevated IU scores across anxiety disorders, depression, and eating disorders. Carleton (2016) has argued that IU may be a “fundamental transdiagnostic fear” underlying neuroticism itself.

Sleep Disturbance

Sleep disturbance is a diagnostic criterion or associated feature of virtually every major psychiatric disorder: approximately 90% of individuals with depression report sleep complaints, nightmares and insomnia are core features of PTSD, sleep disruption both accompanies and triggers bipolar episodes, and sleep disturbance precedes psychotic episodes. Harvey (2008) proposed that sleep disturbance functions as a causal maintaining factor across disorders, not merely a symptom. A landmark RCT by Freeman et al. (2017; N = 3,755) tested this directly: CBT for insomnia delivered to university students not only reduced insomnia but also produced significant reductions in paranoia, hallucinations, anxiety, depression, and nightmares — powerful evidence for the transdiagnostic causal role of sleep.

Interpersonal Dysfunction

Insecure attachment (anxious and avoidant styles) is elevated across virtually all diagnostic categories, with meta-analytic evidence linking it to anxiety (d = 0.37), depression (d = 0.40), personality disorders, eating disorders, and substance use (Bakermans-Kranenburg & van IJzendoorn, 2009). Excessive reassurance-seeking is documented across depression, anxiety, OCD, and health anxiety. Expressed emotion (criticism, hostility, and emotional overinvolvement in families) predicts relapse across schizophrenia, depression, bipolar disorder, and eating disorders (Butzlaff & Hooley, 1998).

The p-Factor and the Hierarchical Taxonomy of Psychopathology (HiTOP)

If transdiagnostic processes suggest that disorders share common mechanisms, quantitative modelling has tried to map that shared structure. Caspi and Moffitt (2014), using data from the Dunedin Multidisciplinary Health and Development Study (a birth cohort of 1,037 individuals followed from birth to age 38), extracted a single general factor — the p-factor (analogous to the g-factor in intelligence) — from the covariance among all forms of psychopathology. Higher p-factor scores were associated with greater life impairment, more extensive family history of mental illness, worse developmental histories, and more compromised brain function. The p-factor was dimensional and normally distributed in the population.

Below the p-factor, three broad spectra emerged: internalising (depression, anxiety, fears), externalising (conduct disorder, substance dependence, antisocial behaviour), and thought disorder (psychotic symptoms, obsessions, mania). This structure has been replicated across multiple large datasets.

The Hierarchical Taxonomy of Psychopathology (HiTOP) (Kotov et al., 2017) formalises this structure into a comprehensive dimensional classification system. HiTOP organises psychopathology hierarchically — from the broad p-factor at the top, through spectra (internalising → distress + fear; externalising → disinhibited + antagonistic; thought disorder; detachment; somatoform), down through subfactors, syndromes, and individual symptoms. Unlike the DSM, HiTOP is empirically derived from factor-analytic studies, dimensional rather than categorical, and naturally accommodates comorbidity by placing co-occurring conditions within the same spectrum.

The Research Domain Criteria (RDoC)

The Research Domain Criteria framework was launched by the NIMH in 2009 under then-director Thomas Insel, motivated by the observation that progress in understanding the neuroscience of mental illness was being impeded by DSM categories that do not map onto underlying biology.

RDoC organises research along a matrix with six functional domains — Negative Valence Systems (fear, anxiety, loss), Positive Valence Systems (reward responsiveness, reward learning), Cognitive Systems (attention, memory, cognitive control), Social Processes (affiliation, social communication), Arousal and Regulatory Systems (arousal, circadian rhythms, sleep), and Sensorimotor Systems — crossed with eight units of analysis: genes, molecules, cells, circuits, physiology, behaviour, self-report, and paradigms.

The key principles are dimensional (psychopathology as the extreme end of normal variation), transdiagnostic (studying constructs like anhedonia rather than diagnoses like MDD), and integrative (studying constructs across multiple biological and psychological levels simultaneously). RDoC is a research framework, not a clinical diagnostic system — it does not replace the DSM for everyday practice. However, RDoC-aligned research has already yielded clinically promising findings: Drysdale et al. (2017, Nature Medicine) used resting-state fMRI connectivity to identify four neurophysiological biotypes of depression with strikingly different responses to TMS therapy.

Network Theory of Psychopathology

Borsboom (2017) proposed a radically different conceptualisation. The traditional latent variable model assumes that symptoms (sad mood, insomnia, fatigue, guilt) are caused by an underlying disease entity (“depression”) — symptoms are passive indicators, like fever indicating infection. Network theory proposes instead that symptoms are causally connected to each other and that the disorder is the network itself. There is no hidden disease behind the symptoms.

In a network model, nodes represent individual symptoms and edges represent causal connections between them. Insomnia causes fatigue, which causes concentration problems, which impairs work performance, which generates feelings of worthlessness, which produces sad mood, which worsens insomnia — a self-reinforcing feedback loop. Bridge symptoms are those that connect different disorder networks, explaining comorbidity: insomnia and fatigue may bridge anxiety and depression networks. Central symptoms — those with many strong connections — function as hubs that, if activated, can cascade through the entire network. Once fully activated, a network can maintain itself even after the original trigger is removed (a property called hysteresis), explaining why disorders persist after stressors resolve.

Network theory offers a natural explanation for comorbidity (bridge symptoms activate adjacent networks), for why some patients respond to specific interventions while others do not (different network structures require different targets), and for why the same diagnosis can look so different across individuals (different network topologies). However, the approach has been criticised for stability issues across samples and for the gap between statistical associations and genuine causal connections.

Barlow’s Unified Protocol

The transdiagnostic insights reviewed above converge on a practical clinical question: if emotional disorders share common mechanisms, can a single treatment target those mechanisms effectively? The Unified Protocol for Transdiagnostic Treatment of Emotional Disorders (UP; Barlow et al., 2011) was designed to do exactly this.

The UP consists of eight modules targeting the shared core of neuroticism/negative affectivity and maladaptive emotional reactions:

The pivotal RCT (Barlow et al., 2017, JAMA Psychiatry; N = 223) compared the UP against single-disorder protocols (SDPs — the gold-standard CBT for each specific disorder) and a waitlist control. The result: the UP was equivalent to SDPs on all primary outcomes. Both active treatments significantly outperformed the waitlist. Critically, participants with comorbid diagnoses showed improvement in non-targeted disorders at rates comparable to their targeted conditions — a benefit that disorder-specific protocols, which treat one condition at a time, cannot match as efficiently. Mediational analyses confirmed that changes in neuroticism mediated the UP’s treatment effects.

Toward Precision Psychiatry

The transdiagnostic revolution points toward a future in which treatment decisions are based on mechanisms rather than diagnoses. DeRubeis et al. (2014) developed the Personalized Advantage Index (PAI) — a statistical model combining multiple patient characteristics to predict which individuals would respond better to CBT versus antidepressant medication for depression. They found that if patients had been assigned to their optimal treatment, outcomes would have improved by approximately 0.30 standard deviations. Drysdale et al. (2017) showed that neural connectivity-based biotypes of depression predicted TMS response rates ranging from 83% (optimal biotype) to below 25% (non-matching biotypes).

Hofmann and Hayes (2019) proposed process-based therapy — selecting treatment techniques based on which transdiagnostic processes are impaired in a given individual rather than which DSM diagnosis they carry. If a patient with comorbid GAD and depression shows primarily rumination and behavioural avoidance as maintaining processes, treatment targets those processes regardless of diagnostic label. This approach directly leverages the transdiagnostic understanding developed throughout this chapter.

The vision is compelling: a psychiatry that asks not “what disorder does this person have?” but “which mechanisms are driving this person’s suffering, and which interventions best target those mechanisms?” We are not there yet — large datasets are needed, biomarker findings have not consistently replicated, and the infrastructure for routine mechanism-based assessment is still developing. But the direction of travel is clear, and it represents the logical conclusion of the integrative, transdiagnostic perspective that has threaded through every chapter of these notes.