Schizophrenia Spectrum and Other Psychotic Disorders
What the exam tests
Psychosis items test symptom domains, duration thresholds, differential diagnosis and antipsychotic safety. You must separate schizophrenia, schizophreniform disorder, brief psychotic disorder, schizoaffective disorder and substance-induced psychosis.
Core rules
- Symptoms are positive (delusions, hallucinations, disorganisation), negative (flat affect, avolition, alogia) and cognitive (attention, memory, executive).
- DSM-5-TR schizophrenia: two or more symptoms, one core symptom, active phase one month and continuous disturbance six months. Brief psychotic disorder is under one month; schizophreniform disorder is one to six months.
- Schizoaffective disorder requires psychosis plus a major mood episode, with delusions or hallucinations for two weeks in the absence of mood symptoms.
- Antipsychotics are first-line; clozapine is for treatment-resistant illness and needs white-cell monitoring. Monitor weight, glucose, lipids and prolactin.
- Catatonia is a syndrome, not a diagnosis, and responds to benzodiazepines or ECT.
Worked example
A 19-year-old has eight months of persecutory delusions, third-person auditory hallucinations and social decline, with no prominent mood episode and no substance use. The duration and symptom pattern fit schizophrenia. The reasoning is that the illness exceeds six months, includes core psychotic symptoms and causes functional decline; brief and schizophreniform disorders are excluded by time.
Traps that cost marks
Do not diagnose schizophrenia from bizarre behaviour alone. Do not overlook mood episodes, substances or medical causes. Do not miss neuroleptic malignant syndrome: rigidity, fever, autonomic instability and raised creatine kinase. Do not use antipsychotics alone for catatonia without assessing cause.