Psychotic disorders and schizophrenia spectrum
The exam tests duration criteria, boundary cases between schizophrenia-spectrum diagnoses, and evidence-based sequencing of treatment.
Core rules
- DSM-5-TR schizophrenia: at least two of delusions, hallucinations, disorganized speech, grossly disorganized or catatonic behaviour, negative symptoms, with at least one from the first three; continuous disturbance for at least six months, including at least one month of active symptoms; functional decline; not due to substance or medical illness.
- Duration ladder: brief psychotic disorder under one month with full return to premorbid function; schizophreniform one to six months; schizophrenia six months or more. Delusional disorder: one month or more of delusions with functioning not markedly impaired and no prominent hallucinations.
- Schizoaffective disorder: a mood episode concurrent with active-phase symptoms, plus at least two weeks of delusions or hallucinations in the absence of a mood episode, with mood symptoms present for most of the total illness duration.
- Prognostic factors: good premorbid adjustment, female sex, later onset, acute onset, short duration of untreated psychosis, family history of mood disorder, and prominent positive symptoms predict better outcome.
- Treatment: antipsychotic monotherapy, lowest effective dose; clozapine after two failed adequate antipsychotic trials (treatment-resistant schizophrenia). Clozapine requires regular absolute neutrophil counts because of agranulocytosis risk (higher in the first six months), plus monitoring for myocarditis, seizures, constipation and sialorrhea.
- Acute dystonia (hours to days) responds to anticholinergics; parkinsonism (weeks); akathisia; tardive dyskinesia (months to years), for which VMAT2 inhibitors (valbenazine, deutetrabenazine) are indicated. Neuroleptic malignant syndrome: hyperthermia, lead-pipe rigidity, autonomic instability, raised CK; stop the drug, cool, use bromocriptine or dantrolene, consider ECT.
Worked example
A 22-year-old man has eight months of persecutory delusions and auditory hallucinations with a six-month period of social withdrawal. Six months of continuous illness places him in schizophrenia rather than schizophreniform disorder, and clozapine is not yet indicated because he has not failed two adequate antipsychotic trials.
Traps
Counting the prodrome wrongly; diagnosing schizophrenia on the first month; starting clozapine first-line; forgetting that catatonia responds to benzodiazepines and ECT rather than more antipsychotic.