More than a quarter of people who experience substance-induced psychosis are diagnosed with schizophrenia within six years, a study in The American Journal of Psychiatry has found.
Eline B. Rognli, Ph.D., of Oslo University Hospital and colleagues analyzed data from 3,187 patients in the Norwegian Patient Registry who were between the ages of 18 and 79 and had a diagnosis of substance-induced psychosis from 2010 to 2015. The patients had a mean age of 33.6 years, and 73.5% were men. Among the patients, 14.2% had alcohol-induced psychosis, 17.6% had cannabis-induced psychosis, 22.2% had amphetamine-induced psychosis, and 38.8% had psychosis induced by multiple substances. The patients were followed from the first diagnosis of substance-induced psychosis in the observation period until a diagnosis of schizophrenia spectrum disorder or bipolar disorder, death, migration, the month they turned 80, or the end of 2015, whichever came first.
Overall, 27.6% of the patients with substance-induced psychosis transitioned to schizophrenia within six years. Men had a higher rate of transitioning to schizophrenia than women: 28.6% among men compared with 24.8% among women. The transition rate was highest for the youngest patients: 32.7% for patients aged 18 to 25 years and 32.9% for patients aged 26 to 30 years. The transition rate was highest for cannabis-induced psychosis and lowest for alcohol-induced psychosis. Among those who transitioned to schizophrenia, 56.4% did so within a year of their diagnosis of substance-induced psychosis.
The researchers also examined the relationship between substance-induced psychosis and bipolar disorder. Overall, 4.5% of patients with substance-induced psychosis transitioned to bipolar disorder within six years. Women had a higher rate of transitioning to bipolar disorder than men: 7.1% among women compared with 3.5% among men. Among those who transitioned to bipolar disorder, 52.0% did so within a year of their diagnosis of substance-induced psychosis.
“Transition rates from substance-induced psychosis to schizophrenia spectrum disorder were six times higher than transition rates to bipolar disorder. … [O]ur findings indicate that substance-induced psychosis, particularly cannabis-induced psychosis, is a major risk factor for schizophrenia, and that younger age among men and repeated emergency admissions are associated with higher risk,” the researchers wrote. “This should inform and guide how … health services provide care for individuals with substance-induced psychosis.”
For related information, see The American Journal of Psychiatry article “Prediction of Onset of Substance-Induced Psychotic Disorder and Its Progression to Schizophrenia in a Swedish National Sample.”
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