Episodes of substance-induced psychosis are common in emergency departments and crisis centers. There are many precipitating substances, including alcohol, amphetamines, cannabis, cocaine, hallucinogens, opioids, phencyclidine (PCP), and sedative/hypnotics. To be considered substance-induced psychosis, the hallucinations and delusions should be in excess of those that typically accompany simple substance intoxication or withdrawal, although the patient may also be intoxicated or withdrawing.
Symptoms are often brief, resolving shortly after the causative drug is cleared, but psychosis triggered by amphetamines, cocaine, or PCP may persist for many weeks. Because some young people with prodromal or early-stage schizophrenia use substances that can induce psychosis, it is important to obtain a thorough history, particularly to seek evidence of prior mental symptoms before concluding that acute psychosis is due to substance use.
For psychosis due to dopamine-stimulating drugs such as amphetamine, an antipsychotic drug is most effective.
For psychosis due to drugs such as lysergic acid diethylamide (LSD), quiet observation may be all that is needed.
For substances with actions that do not involve dopamine, observation may be all that is needed, or an anxiolytic may help.