Schizophrenia Spectrum and Other Psychotic Disorders
This domain tests accurate syndromal diagnosis across the psychosis spectrum, the distinction between primary and secondary psychosis, and evidence-based treatment including clozapine.
Diagnostic boundaries
Schizophrenia requires two or more core symptoms (delusions, hallucinations, disorganised speech, grossly disorganised or catatonic behaviour, negative symptoms) present for a significant portion of at least six months, with functional decline and exclusion of mood disorder, substance and medical causes. ICD-10 gives weight to first-rank symptoms and uses shorter duration requirements, so the same patient can meet one system and not the other.
- Schizophreniform disorder: one to six months.
- Brief psychotic disorder: less than one month with full return to premorbid function.
- Delusional disorder: delusions for at least one month, functioning otherwise preserved, behaviour not obviously odd.
- Schizoaffective disorder: mood episode plus psychotic symptoms, with at least two weeks of delusions or hallucinations in the absence of a mood episode.
Secondary psychosis must be excluded
Temporal lobe epilepsy, Wilson disease, SLE, thyrotoxicosis, B12 deficiency, steroid and dopamine agonist use, delirium, and stimulant or cannabis intoxication.
Treatment rules
Start an antipsychotic at an adequate dose; response usually appears within two to four weeks. Treatment-resistant schizophrenia means two adequate trials of different antipsychotics with poor response, and the next step is clozapine. Add family intervention and CBT for psychosis. Shorter duration of untreated psychosis predicts better outcome; so do acute onset, good premorbid function, later onset and female sex. Catatonia responds to benzodiazepines, typically lorazepam challenge, with ECT for refractory cases.
Worked example
A 21-year-old has four months of persecutory delusions and auditory hallucinations, with two weeks of depressed mood at the start. Reasoning: the psychotic symptoms substantially exceed the mood episode in duration and the mood is not present for most of the illness, so schizoaffective disorder is not justified and schizophrenia is the better fit once organic and substance causes are excluded.
Traps that cost marks
Diagnosing schizophrenia after two months of symptoms. Missing a substance-induced or organic psychosis. Calling negative symptoms depression without assessing anhedonia, avolition and affect separately. Continuing a failing antipsychotic instead of moving to clozapine. Forgetting metabolic monitoring on antipsychotics.