Drug-Induced Psychosis

Essential Concepts

Some drugs of abuse cause psychosis during intoxication (or during withdrawal in the case of alcohol or sedative-hypnotics). Prolonged psychosis is typical for phenylcyclohexylpiperidine (PCP) and methamphetamines.
History of drug ingestion supported by urine drug testing and resolution of symptoms in a manner characteristic for the drug suggests a drug-induced psychosis.
Chronic alcoholism can cause chronic psychosis in the form of alcoholic hallucinosis and delusional jealousy (Othello syndrome).
Cannabis increases the risk of eventually being diagnosed with schizophrenia sixfold. It is unclear if cannabis triggers an illness that would have never occurred or merely pushes the onset into earlier ages.
Stimulants and hallucinogens predictably cause a short-lived, drug-induced psychosis (except for methamphetamine psychosis, which can last weeks).
PCP can cause a severe, agitated psychosis lasting many days.

“Drugs are a bet with your mind.”

—Jim Morrison, The Doors, 1943-1971

Many drugs can cause psychosis (delusions and/or hallucinations) in a clear sensorium (i.e., in the absence of a delirium). This is true not only for legal drugs (e.g., alcohol) or illegal drugs but also for prescribed medications (e.g., steroids or digoxin), herbal medications, and over-the-counter medications. In this chapter, I discuss patients who present to the emergency department (ED) with drug-induced psychosis. For a discussion of drug abuse in schizophrenia, see the chapter on dual diagnosis (Chapter 23).

DIAGNOSIS OF DRUG-INDUCED PSYCHOSIS

Some drugs predictably induce psychosis in most individuals after single use: PCP and lysergic acid diethylamide (LSD) are examples. Some drugs do so only in a small minority of patients (cannabis), or after prolonged use (cocaine). The major drugs that cause psychosis during withdrawal are alcohol and the sedative-hypnotics (barbiturates and benzodiazepines), as well as one of the club drugs, γ-hydroxybutyrate (GHB) (Table 4.1). Opiates as a rule of thumb are not associated with psychosis, although exceptions exist.

The diagnosis of drug-induced psychosis is somewhat complex, and one must look at history of drug use, symptoms, and results of urine drug testing. Ideally, a 4-week period of abstinence is necessary to judge if psychosis resolves in a time course consistent with the drug. Unfortunately, the necessary abstinence period is frequently not achieved, and you are left wondering how much psychosis is fueled by intermittent, low-grade drug use.

History of Drug Use

The history of drug use might be unavailable or incomplete. Patients themselves might not know what they ingested, or whether they were taking adulterated drugs (e.g., cannabis with PCP). Therefore, urine drug testing is mandatory even in cases in which a specific drug or no drug use is reported.

TABLE 4.1. Drug-Induced Psychosis

	During Intoxication	During Withdrawal	Prolonged
Alcohol	Yes	Yes	Yes
Sedatives	Yes	Yes	Yes
Cannabis	Yes	No	Not usually
Stimulants	Yes	No	Yes (methamphetamine)
Hallucinogens	Yes	No	Not usually
PCP	Yes	No	Yes
Opiates	Not usually	Not usually	Not usually