Schizophrenia

• Dopamine Hypothesis (Revised): The classical dopamine hypothesis originally attributed schizophrenia to generalized dopamine excess; however, contemporary models propose hyperdopaminergia in mesolimbic pathways (ventral tegmental area to nucleus accumbens) paired with hypodopaminergia in mesocortical projections (ventral tegmental area to prefrontal cortex). Mesolimbic hyperactivity generates positive symptoms (hallucinations, delusions) via excessive reward prediction error signaling and aberrant salience attribution to neutral stimuli. Conversely, prefrontal cortical dopamine depletion impairs working memory, attention, and executive function, manifesting as negative symptoms (avolition, cognitive deficits) and disorganized behavior. This dissociation explains why dopamine D2 receptor antagonists effectively suppress positive but not negative symptoms. The involvement of both D1 and D2 receptors across these circuits creates a physiological basis for symptom heterogeneity and differential treatment response.

• Glutamatergic Dysfunction and the N-Methyl-D-Aspartate (NMDA) Receptor Hypothesis: Convergent evidence implicates hypofunction of NMDA glutamate receptors, particularly on GABAergic interneurons in the prefrontal cortex and anterior cingulate. NMDA receptor hypofunction reduces GABAergic inhibition of pyramidal neurons, paradoxically increasing overall cortical glutamate release and producing excitotoxicity. This cascade disrupts thalamic-cortical information gating, impairs working memory networks, and destabilizes reality testing. Phencyclidine (PCP) and ketamine, which are NMDA antagonists, reliably induce psychotic states in humans, providing direct experimental evidence for this mechanism. Additionally, genetic variants in COMT (catechol-O-methyltransferase), which metabolizes dopamine and affects prefrontal dopamine-glutamate interactions, modulate schizophrenia risk and cognitive performance.

• Neurodevelopmental Abnormalities: Schizophrenia involves disruption of normal cortical development during late childhood and early adulthood, particularly synaptic pruning during adolescence. Normally, synaptic density peaks in childhood and undergoes selective elimination during adolescence, refining neural circuits. In schizophrenia, aberrant pruning patterns—characterized by excessive elimination of glutamatergic synapses in prefrontal regions—compromise cognitive and emotional regulation circuits. Decreased gray matter volume in the prefrontal cortex, anterior cingulate, and temporal regions correlates with cognitive deficits and symptom severity. Additionally, white matter abnormalities (reduced myelination, altered fractional anisotropy) in frontal-temporal tracts disrupt long-range connectivity essential for coherent thought and perception.

• Genetic and Epigenetic Factors: Schizophrenia is highly heritable (heritability ~64%), with genome-wide association studies (GWAS) identifying multiple polygenic loci conferring modest individual risk. Key risk variants involve neurodevelopmental processes: DISC1 (Disrupted in Schizophrenia 1) affects neuronal migration and synaptic plasticity; NRG1/ErbB4 signaling modulates GABAergic function and dopamine release; complement component 4 (C4) variants increase synaptic pruning by innate immune mechanisms. Epigenetic modifications (DNA methylation, histone acetylation) regulate expression of schizophrenia-risk genes in response to prenatal and early life stressors. These molecular mechanisms explain the incomplete penetrance of genetic risk and why environmental factors are necessary for disease manifestation.

• Inflammatory and Immune Dysregulation: Emerging evidence indicates elevation of pro-inflammatory cytokines (IL-6, TNF-α, IL-1β) in the serum and cerebrospinal fluid (CSF) of schizophrenia patients, particularly during acute psychotic episodes. Maternal infection during pregnancy (viral or bacterial) increases offspring schizophrenia risk via transplacental transfer of inflammatory mediators and microglial activation. Microglia (brain-resident innate immune cells) appear hyperactivated in schizophrenia, contributing to excessive complement-mediated synaptic pruning and neuroinflammation. This immunopathological component may explain treatment-resistant cases and the subset of schizophrenia patients who respond to anti-inflammatory adjunctive therapies (e.g., NSAIDs).

• Thalamic Dysfunction and Sensory Gating Deficits: The thalamus acts as a critical "gating" structure, filtering sensory information and modulating cortical input. In schizophrenia, thalamic filtering is impaired, resulting in cognitive overload and intrusive perceptual experiences. Reduced GABAergic inhibition from the reticular nucleus to relay nuclei allows excessive sensory throughput to cortex. This mechanism underlies prepulse inhibition (PPI) deficits observed in schizophrenia patients and animal models—the failure to suppress startle response to a strong stimulus when preceded by a weak prepulse. PPI deficits correlate with positive symptom severity and may represent an endophenotype reflecting underlying neural dysfunction.

• Disturbed Interoception and Predictive Coding: Contemporary computational models propose that schizophrenia involves aberrant prediction error computation—the brain's failure to accurately estimate expected sensory input and compare it to actual perception. Hyperactive prediction errors in mesolimbic dopamine neurons cause the brain to assign excessive salience (importance) to random or mundane stimuli, generating delusions and hallucinations as post-hoc explanatory narratives. Simultaneously, dampened prediction errors in cortical regions impair learning and adaptation, contributing to cognitive rigidity and negative symptoms.

• Genetic Predisposition: Family history confers substantial risk—first-degree relatives of affected individuals have ~10% lifetime risk, monozygotic twins ~45%, and general population ~1%. No single causative gene exists; instead, multiple common variants of small effect size (polygenic inheritance) and rare de novo mutations (CNVs, copy number variations) collectively determine susceptibility. Notable high-penetrance loci include 22q11 deletion (DiGeorge syndrome; schizophrenia prevalence 20–30%), 1q21 deletion, and 16p11 duplication. The polygenicity explains why genetic testing is not diagnostically useful; polygenic risk scores may eventually aid risk stratification.

• Prenatal and Perinatal Factors: Maternal infection during second trimester (influenza, toxoplasmosis, rubella) is robustly associated with offspring schizophrenia risk via immune-mediated neurotoxicity. Obstetric complications (hypoxia-ischemia, prematurity, low birth weight, emergency cesarean delivery) expose the developing fetal brain to ischemic and inflammatory insults. Maternal nutritional deficiencies (folate, vitamin D) during pregnancy impair fetal neurogenesis. Maternal stress and cortisol elevation during gestation may epigenetically reprogram HPA axis and dopamine system development.

• Environmental Stressors and the Stress-Vulnerability Model: The stress-vulnerability model posits that schizophrenia emerges when environmental stressors exceed an individual's neurobiological coping capacity. Relevant stressors include: (1) cannabis use (particularly THC-dominant strains), which impairs glutamatergic-dopaminergic balance and increases psychosis risk 3–4 fold, especially in adolescents; (2) childhood trauma and abuse (physical, sexual, emotional), which sensitize HPA axis and increase salience attribution; (3) psychosocial stressors (migration, urbanicity, social disadvantage, social defeat); (4) substance use (amphetamines, cocaine) triggering dopamine surges in susceptible individuals. The "two-hit hypothesis" proposes that genetic vulnerability plus postnatal environmental insult(s) are necessary for disease emergence.

• Neurodevelopmental Abnormalities and Subtle Prodromal Features: Individuals with schizophrenia often exhibit subtle premorbid developmental deviations: motor milestones delays, speech abnormalities, social withdrawal, behavioral oddities, and poor academic performance in childhood. These likely reflect early-life expression of the underlying neurodevelopmental pathology. Recognition of prodromal symptoms (attenuated psychotic symptoms, cognitive decline, social withdrawal lasting weeks to months) identifies a high-risk state with 25–30% transition to full psychosis within 2–3 years.

• Other Contributing Factors: Additional risk modifiers include male sex (earlier onset, worse prognosis), family history of psychiatric illness (increases polygenic risk load), low socioeconomic status (stress exposure, reduced access to protective factors), urbanicity (increased psychosocial stressors, reduced social cohesion), and autoimmune conditions (potential shared inflammatory pathways).

• Positive Symptoms (Additions to Normal Experience):
• Hallucinations: Perception without external stimulus, most commonly auditory hallucinations (70–80% of patients)—typically experienced as voices commenting on behavior, conversing with one another, or commanding harmful acts. The neurobiological basis involves aberrant speech perception attribution coupled with reduced self-monitoring capacity. Second most common are visual hallucinations (30–40%), followed by tactile, olfactory, and gustatory (less frequent, suggest possible organic etiology). Hallucinations are not unique to schizophrenia (occur in mood disorders with psychosis, delirium, neurodegenerative diseases) but are highly distressing and functionally disabling.

• Delusions: Fixed false beliefs resistant to contradictory evidence, arising from aberrant prediction error processing. Common themes include: (1) persecutory delusions (belief that others intend harm)—most frequent, occurring in >80% of psychotic episodes; (2) delusions of reference (belief that unrelated events have personal significance); (3) grandiose delusions (inflated self-importance); (4) somatic delusions (false belief of bodily dysfunction); (5) nihilistic delusions (belief in nonexistence of self or others); (6) thought insertion/withdrawal (belief that thoughts are placed or removed by external agents). Delusions differ from overvalued ideas in their absolute conviction and resistance to reality testing.

• Disorganized Speech: Manifests as tangentiality (answers adjacent to questions), circumstantiality (excessive peripheral detail), derailment (loss of logical thread), incoherence (unintelligible speech), or neologisms (invented words). Results from impaired prefrontal-striatal connectivity compromising verbal working memory and linguistic planning. Severity ranges from mild loosening of associations to complete unintelligibility ("word salad").

• Disorganized or Catatonic Behavior: Includes purposeless agitation, unpredictable violence, bizarre clothing/grooming, social disinhibition, or catatonia—a severe motor disturbance characterized by waxy flexibility (limbs maintain imposed postures), mutism, negativism, echolalia (repetition of others' speech), or posturing. Catatonia, while classically associated with schizophrenia, is now recognized as a non-specific neuropsychiatric sign seen in mood disorders, neurological conditions, and medical illnesses.

• Negative Symptoms (Diminution of Normal Experience):
• Alogia: Poverty of speech—reduced verbal output and spontaneity with brief, non-elaborated responses.

• Avolition/Apathy: Profound loss of motivation and goal-directed behavior; patients lack initiative for self-care, occupational pursuits, or social engagement.

• Anhedonia: Markedly diminished pleasure from previously enjoyed activities; reward processing is dampened via prefrontal-ventral striatal pathway dysfunction.

• Affective Flattening: Restricted range and intensity of emotional expression; facial expression, vocal modulation, and gestural expressiveness are diminished, yet internal emotional experience may be preserved (distinguishing from true depression). Reflects reduced dopamine in anterior insula and ventromedial prefrontal regions.

• Asociality: Withdrawal from social engagement and reduced desire for interpersonal contact.

• Cognitive Symptoms:
• Working memory impairment: Reduced capacity to transiently hold and manipulate information; underlies poor performance on digit span and N-back tasks.

• Executive dysfunction: Deficits in planning, problem-solving, cognitive flexibility (perseveration), and inhibitory control.

• Attention/concentration impairment: Difficulty sustaining focus, increased distractibility.

• Processing speed reduction: Slowed mental processing across multiple cognitive domains.

• Physical Examination Findings:
• Abnormal involuntary movements: May reflect extrapyramidal side effects (dystonia, akathisia, parkinsonism) from antipsychotic treatment or rarely, catatonia.

• Reduced eye contact and altered gaze patterns: Often apparent during interview.

• Neurological soft signs: Increased prevalence of minor neurological abnormalities (dysdiadochokinesia, stereognosis, graphesthesia, balance impairment, mirror movements)—reflect neurodevelopmental abnormalities and correlate with symptom severity.

• Reduced startle prepulse inhibition: Demonstrated in laboratory settings, represents failure to suppress extraneous sensory input.

• Important Clinical Variants:
• Catatonic Type: Features prominent catatonic features (now rare in developed countries with early antipsychotic treatment).

• Paranoid Type: Dominated by persecutory delusions and hallucinations with relatively preserved cognitive and social function.

• Disorganized Type: Characterized by marked disorganization, incoherence, flat/inappropriate affect; often has earlier onset and poorer prognosis.

• Undifferentiated Type: Does not fit neatly into above categories.

• First-Episode Psychosis (FEP): Initial presentation of psychotic symptoms; represents critical window for intervention when neurobiological changes and functional impairment may be partially reversible. Early intervention programs targeting FEP show superior long-term outcomes compared to standard care.

• DSM-5 Diagnostic Criteria: Schizophrenia requires (1) presence of two or more active-phase symptoms for at least 1 month (or less if successfully treated), with at least one being a first-rank positive symptom (delusions, hallucinations, disorganized speech); (2) reduced social/occupational functioning since symptom onset; (3) continuous signs for at least 6 months, including at least 1 month of active symptoms plus up to 5 months of prodromal or residual symptoms; (4) exclusion of schizoaffective disorder (concurrent mood episodes) and exclusion of medical etiologies or substance-induced psychosis. Importantly, two negative/cognitive symptoms alone cannot meet criterion 1—at least one hallucination, delusion, or disorganized speech is mandatory. This distinction is critical for boards.

• Comprehensive Diagnostic Approach:

1. 1.Detailed psychiatric history: Timeline of symptom onset (prodromal vs. acute), characterization of hallucinations and delusions, functional decline trajectory, past episodes, treatment responses, substance use history (cannabis, stimulants, hallucino

Acute stabilisation

• Safety first: assess suicidality, homicidality, and capacity; the APA 2020 Practice Guideline for the Treatment of Patients With Schizophrenia frames hospitalisation around dangerousness and inability to care for self. Screen for substance intoxication/withdrawal and medical mimics before committing to a diagnosis.
• Acute agitation: a high-potency first-generation antipsychotic (haloperidol) or a second-generation agent (olanzapine, ziprasidone) IM, often with a benzodiazepine (lorazepam) for rapid sedation. Do not combine IM olanzapine with parenteral benzodiazepines — the FDA labeling warns of excessive sedation and cardiorespiratory depression.
• Catatonia: a lorazepam challenge first; electroconvulsive therapy if refractory. Antipsychotics alone may worsen catatonia and raise neuroleptic malignant syndrome risk.

First-line maintenance therapy

• Any single antipsychotic (D2 antagonist or partial agonist): APA 2020 recommends antipsychotic monotherapy with the agent chosen by side-effect profile, prior response, and patient preference rather than by presumed class superiority — a lesson of the CATIE trial. Representative agents: risperidone, aripiprazole (D2 partial agonist), olanzapine. Blocking mesolimbic D2 transmission dampens aberrant salience and thus positive symptoms; negative and cognitive symptoms respond poorly.
• Adequate trial: therapeutic dose for several weeks before declaring failure.
• Long-acting injectables: paliperidone palmitate, aripiprazole lauroxil — APA suggests these for nonadherence or patient preference, the leading modifiable driver of relapse.

Escalation and treatment resistance

• Clozapine: indicated after failure of two adequate antipsychotic trials, and also recommended when suicide risk or persistent aggression dominates. It is the only agent with established superiority in treatment-resistant illness.
• ECT: adjunct for clozapine-refractory psychosis and for catatonia.
• Xanomeline–trospium, a muscarinic M1/M4 agonist paired with a peripherally restricted antagonist, is a newer FDA-approved non-D2 option.

Non-pharmacologic and contraindications

• Coordinated specialty care for first-episode psychosis (NIMH RAISE model), plus CBT for psychosis, family psychoeducation, assertive community treatment, and supported employment — all APA-endorsed.
• Avoid: routine antipsychotic polypharmacy and routine prophylactic anticholinergics; antipsychotics carry an FDA boxed warning for increased mortality in dementia-related psychosis.

Disease-related

• Suicide: the leading cause of premature death early in the illness; risk peaks in young patients with preserved insight, recent discharge, or command hallucinations. Emergency — clozapine is the antipsychotic with evidence for reducing suicidal behavior.
• Premature cardiovascular mortality: schizophrenia shortens life expectancy by roughly two decades, driven by smoking, sedentary behavior, poor preventive care, and antipsychotic metabolic effects.
• Comorbid substance use, homelessness, incarceration, and victimization — patients are far more often victims than perpetrators of violence.
• Psychogenic polydipsia: signalled by hyponatremia with dilute urine, seizures. Emergency if severe.

Treatment-related — emergencies

• Neuroleptic malignant syndrome: idiosyncratic D2 blockade in nigrostriatal and hypothalamic pathways → lead-pipe rigidity, hyperthermia, autonomic instability, altered mental status, markedly elevated creatine kinase, leukocytosis. Stop the drug, cool aggressively, supportive care ± dantrolene or bromocriptine. Emergency.
• Clozapine-induced severe neutropenia/agranulocytosis: immune-mediated marrow toxicity; signalled by fever/sore throat with a falling absolute neutrophil count. ANC monitoring is mandated by the FDA Clozapine REMS. Emergency.
• Clozapine myocarditis: typically within the first weeks; tachycardia, fever, eosinophilia, rising troponin and CRP. Emergency.
• Clozapine-induced gastrointestinal hypomotility: potent anticholinergic effect → severe constipation, ileus, bowel perforation. Emergency.
• QT prolongation and torsades: ziprasidone, IV haloperidol, thioridazine; watch for hypokalemia/hypomagnesemia. Emergency.
• Acute dystonia: hours to days after initiation; oculogyric crisis or laryngospasm — treat with anticholinergic (benztropine) or diphenhydramine. Laryngeal involvement is an emergency.

Treatment-related — chronic

• Metabolic syndrome: H1/5-HT2C-mediated weight gain and insulin resistance, worst with olanzapine and clozapine; the ADA/APA consensus on antipsychotics and metabolic risk advises baseline and serial weight, glucose/A1c, and lipid monitoring.
• Hyperprolactinemia: tuberoinfundibular D2 blockade (risperidone, paliperidone) → galactorrhea, amenorrhea, sexual dysfunction, reduced bone density.
• Akathisia: inner restlessness, pacing; associated with suicidality. Reduce dose or add a beta blocker (propranolol).
• Tardive dyskinesia: chronic D2 blockade with receptor upregulation → orofacial choreoathetosis, often irreversible; treat with a VMAT2 inhibitor (valbenazine, deutetrabenazine).
• Clozapine-lowered seizure threshold, dose-dependent, and sialorrhea.

• The duration ladder is the single most tested fact: symptoms lasting < 1 month = brief psychotic disorder; 1–6 months = schizophreniform disorder; ≥ 6 months of continuous signs = schizophrenia. Delusional disorder requires ≥ 1 month of delusions with otherwise preserved functioning.
• Schizoaffective disorder is the classic distractor: it requires delusions or hallucinations for ≥ 2 weeks in the absence of a major mood episode. If psychosis occurs only during mood episodes, the answer is major depression or bipolar disorder with psychotic features.
• Best next step in a first psychotic episode: exclude organic and substance causes — urine toxicology (stimulants, cannabis, PCP), metabolic panel, TSH, and neuroimaging if focal signs or atypical features (visual, olfactory, or tactile hallucinations should push you toward delirium, temporal lobe seizure, or intoxication).
• Clozapine is the answer whenever the stem gives two failed adequate antipsychotic trials, and also when persistent suicidality is emphasized. The examiner then wants absolute neutrophil count monitoring under the FDA Clozapine REMS. New fever with sore throat on clozapine → check ANC; chest pain and tachycardia in the first weeks → myocarditis.
• NMS versus serotonin syndrome: NMS evolves over days with lead-pipe rigidity and hyporeflexia after a D2 blocker; serotonin syndrome evolves over hours with clonus, hyperreflexia, and diarrhea after a serotonergic agent.
• Akathisia is the trap: restlessness mistaken for worsening psychosis. Increasing the antipsychotic dose is the wrong answer; lower the dose or add propranolol.
• Movement side-effect pairing: acute dystonia → benztropine; tardive dyskinesia → VMAT2 inhibitor (valbenazine). Anticholinergics worsen tardive dyskinesia — a favorite distractor.
• The one association examiners love: 22q11.2 deletion syndrome and markedly elevated schizophrenia risk; also, catatonia in a schizophrenia stem → lorazepam challenge first, ECT if refractory.
• Prognosis pearls: acute onset, later onset, prominent mood symptoms, and good premorbid function predict better outcome; insidious onset with prominent negative symptoms predicts worse outcome.