The structured differential (organic → functional)
This is the disciplined workflow from Concept 7, applied:
- Organic/medical — delirium, encephalitis (incl. autoimmune/anti‑NMDA‑R), epilepsy, CNS lesion, endocrine/metabolic, B12, HIV/neurosyphilis. Flags: altered/fluctuating consciousness, inattention, visual hallucinations, focal signs, atypical age.
- Substance‑induced — stimulants, cannabis/synthetics, hallucinogens, and withdrawal states; apply the timeline principle.
- Mood disorder with psychotic features — psychosis confined to mood episodes, typically mood‑congruent.
- Primary psychotic disorders — differentiate within the spectrum (below).
"Organic vs functional" — use, but don't misuse
"Functional" ≠ "imaginary." It denotes disorders without an identified structural/medical cause as the primary driver; the neurobiology is real. The clinically useful move the dichotomy encodes: actively exclude organic disease before committing to a primary psychotic diagnosis.
Within the spectrum — key discriminators
- Schizophrenia vs schizophreniform: identical cross‑section; duration differs (≥6 months incl. prodrome/residual vs 1–6 months).
- Brief psychotic disorder: <1 month, often post‑stressor, full return to baseline.
- Schizoaffective: concurrent mood + psychotic criteria, but *≥2 weeks of psychosis without prominent mood symptoms* (this criterion is what separates it from mood disorder with psychosis).
- Delusional disorder: encapsulated non‑bizarre delusion(s), function preserved outside the delusional theme, without the broader disorganisation/negative‑symptom load of schizophrenia.
Placing a patient within the spectrum (organic & substance already excluded):
Delirium vs primary psychosis — the time‑critical split
Acute onset + fluctuating attention + altered arousal + prominent cognitive disturbance ⇒ delirium/medical until excluded. Consciousness, attention, and time course are the discriminators (expanded in Concept 15).
Pitfalls
- Anchoring on schizophrenia at first contact; missing an affective or organic cause that would change first‑line treatment entirely.
- Diagnosing schizoaffective loosely — it requires the specific temporal relationship, not merely "mood + psychosis."
Pearls
- 🎯 "Why is this patient psychotic?" is the whole concept in one question.
- 🩺 Duration and the mood–psychosis temporal relationship are the two levers that move you across the spectrum.
Next → Characterise the two cardinal positive symptoms with the precision that discriminates — delusions (Concept 10) and hallucinations (Concept 11).