Substance-induced psychotic disorder is the diagnosis when psychotic symptoms are directly caused by substance use, intoxication, or withdrawal. The DSM-5 criteria require evidence that symptoms developed during or soon after substance intoxication/withdrawal and that the involved substance is capable of producing the symptoms. The differential that must be ruled out before committing to primary psychotic illness diagnosis.
Major substances and their characteristic patterns:
Stimulants (methamphetamine, cocaine, amphetamines): paranoid delusions, auditory and tactile hallucinations (classic "formication" — sense of bugs crawling on skin), with chronic use can produce persistent psychosis lasting weeks to months. Heavy methamphetamine use is the largest contributor to substance-induced psychosis in current US epidemiology.
Cannabis: particularly high-potency cannabis and adolescent use. Acute psychotic symptoms during or after use; chronic heavy use associated with increased risk of persistent psychotic illness in genetically vulnerable individuals.
Alcohol: delirium tremens (life-threatening alcohol withdrawal with autonomic instability, hallucinations, delirium) and alcoholic hallucinosis (auditory hallucinations during heavy use or early withdrawal with preserved sensorium).
Corticosteroids: steroid-induced psychosis, particularly at high doses (prednisone >40 mg/day equivalent). Often paranoid, sometimes manic. Can develop days to weeks into therapy.
Anticholinergics: classic anticholinergic toxidrome — confusion, visual hallucinations, agitation. Particularly in older patients.
Dopamine agonists: prescribed for Parkinson's disease and restless legs syndrome — can produce visual hallucinations and psychotic symptoms, sometimes with impulse control problems.
The workup that must happen: comprehensive toxicology screen, history of all recent medication changes, alcohol and substance use history including supplements and herbals, careful timeline of symptom onset relative to substances. Substance-induced psychosis is the diagnosis to rule out before committing to primary psychotic illness because management differs substantially.
Management: treat the substance issue — withdrawal management for alcohol/sedatives, abstinence support for stimulants, taper of offending medication when possible. Acute psychotic symptoms often resolve with abstinence over days to weeks. Brief antipsychotic for acute agitation or persistent symptoms during abstinence. Watch for persistence beyond 1 month of abstinence — this may unmask primary psychotic illness or suggest persistent stimulant-induced psychosis.
When you encounter a patient with new psychotic symptoms, particularly young adults or older patients with medication changes, substance-induced and medication-induced psychosis are the first differentials. The workup catches reversible causes; committing too quickly to primary psychiatric diagnosis is the common error.