Acute Marijuana-Induced Psychosis May Predict Future Illness

Some individuals experience acute psychotic symptoms that are time-linked to ingesting a recreational drug. These symptoms usually resolve within a few days or a week. However, recent evidence indicates that a significant percentage of these people later develop a chronic psychotic illness.

In a potentially important study published in the American Journal of Psychiatry, Marie Stephanie Kejser Starzer, Merete Nordentoft, and Carsten Hjorthøj report on the long-term outcome of individuals who are diagnosed with substance-induced psychosis. They utilize data from the Psychiatric Central Research Register in Denmark, which has records of all inpatient psychiatric treatment since 1969 and all outpatient treatment since 1995. This database allows for decades of longitudinal data to be examined.

For this study, the investigators reviewed the long-term outcomes of all persons who received a diagnosis of substance-induced psychosis between 1994 and 2014 and had no prior diagnosis of a psychotic illness — a group of over 6,700 people. The diagnosis of drug-induced psychosis required symptoms lasting at least 48 hours — linked to intoxication with or withdrawal from the drug.

When the investigators compared this group with a large group of appropriately matched controls, they found a striking increase in the development of either schizophrenia or bipolar disorder in those who had experienced acute psychotic episodes after taking alcohol, opioids, cannabis, sedatives, cocaine, amphetamines, and/or hallucinogens. The most dramatic increases by far occurred in those who exhibited psychotic symptoms following marijuana use.

Over a twenty-year follow-up period, about 41 percent of those who had a psychotic reaction to marijuana developed schizophrenia, and 47 percent developed either schizophrenia or bipolar disorder. About half of those who developed schizophrenia did so within 3.1 years, and half of those who developed bipolar disorder did so within 4.4 years.

Most people who use marijuana don’t develop an acute psychosis lasting several days. However, for those who do, the risk of developing schizophrenia or bipolar disorder is frighteningly high (almost 50 percent). Why? It is possible that individuals who are already predisposed to develop schizophrenia or bipolar disorder are more likely to become acutely psychotic when using abused substances, especially marijuana. Other data have shown that those who use marijuana heavily, especially in their early adolescent years, develop schizophrenia at a much higher rate than can be explained by genetic predisposition.

These results demonstrate that those who are diagnosed with substance-induced psychotic symptoms, especially after marijuana use, are at high risk for eventually developing a chronic psychotic illness. This usually occurs several years down the road. Can the process of developing clinical symptoms be delayed or even prevented? Should individuals who experience substance-induced psychosis be more closely followed by mental health professionals?

It is possible that future studies of individuals who develop acute psychotic symptoms in response to abused substances could help define markers of illnesses before the illnesses manifest clinically. The more we understand about the pre-symptomatic phase of illnesses, the more likely preventative interventions can be developed.

This column was written by Eugene Rubin MD, PhD and Charles Zorumski MD.