The diagnostic architecture (DSM‑5, in reasoning form)
- ≥2 of {delusions, hallucinations, disorganised speech, grossly disorganised/catatonic behaviour, negative symptoms}, at least one being a core positive symptom (delusions, hallucinations, or disorganised speech).
- Duration ≥6 months total, with ≥1 month of active‑phase symptoms.
- Functional decline from premorbid baseline.
- Exclusions: schizoaffective and mood‑with‑psychosis ruled out; not attributable to a substance or another medical condition.
The eight longitudinal questions
Onset · course (continuous/episodic) · functional trajectory · relationship to mood episodes · substance exposure · medical/neurological clues · prior episodes · risk (self‑harm, violence, neglect, command hallucinations). These are what convert a cross‑sectional snapshot into a diagnosis.
First‑episode psychosis (FEP) — the practical priority
FEP is a workup event, not a label to apply hastily: full medical screen, toxicology, consider neuroimaging/EEG/autoimmune antibodies where atypical. Duration of untreated psychosis (DUP) predicts outcome — early, decisive assessment and treatment matter. Preserve the differential; a substantial minority will declare themselves affective or organic over time.
Pitfalls
- Applying "schizophrenia" before the 6‑month duration is met (it may be schizophreniform/brief psychotic).
- Missing an evolving bipolar or organic picture at first episode.
Pearls
- 🎯 Diagnosis = cross‑section + duration + functional decline + exclusions. All four, or it isn't schizophrenia yet.
- 🩺 Minimise DUP — it's one of the few outcome levers you control at first contact.
Next → When you treat, predict effects from mechanism — antipsychotic pharmacology (Concept 13).