The timeline principle (the whole concept)
Substance‑induced disorders (psychosis, mood, anxiety, delirium) are defined by their temporal relationship to use. Establish: substance, dose, frequency, time of last use, symptom onset relative to use, persistence during sustained abstinence, and any prior episodes independent of substances.
Induced vs primary — and the trap
- Substance‑induced: tight temporal link; typically resolves within days–weeks of abstinence.
- Primary psychotic disorder: independent course; persists beyond the expected substance window.
- The trap: "drugs are involved, so it can't be schizophrenia." False. Cannabis (esp. heavy, high‑potency, early‑onset) is a risk factor for later schizophrenia‑spectrum illness; substance‑induced psychosis has a substantial conversion rate to a primary disorder. Diagnose longitudinally, and re‑evaluate — persistence beyond abstinence reclassifies it.
Practically
Don't over‑commit at first contact; document the timeline, ensure follow‑up through an abstinence period, and treat the acute psychosis regardless of presumed cause.
Pitfalls
- Using drug use to exclude a primary psychotic disorder.
- Failing to follow up to see whether psychosis persists beyond abstinence.
Pearls
- 🎯 Chronology is diagnostic evidence.
- 🩺 Persistence beyond abstinence is what converts "induced" into "primary."
Next → Enduring patterns in modern (dimensional) framing (Concept 46).