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One-third of adults with substance-induced psychosis convert to schizophrenia, bipolar disorder

Recent findings indicated a strong association between substance-induced psychosis and conversion to schizophrenia and bipolar disorder, suggesting a need for long-term follow-up to identify most cases.

“New findings suggest that a large number of patients with a substance-induced psychosis later develop chronic psychotic conditions,” Marie Stefanie Kejser Starzer, MD, of Copenhagen University Hospital, Denmark, and colleagues wrote. “Psychiatric patients who also have a substance abuse problem are often diagnosed later than those with no substance abuse, and consequently treatment is delayed. It would be of great interest to identify those at high risk so that treatment could be initiated earlier.”

To determine conversion rates to schizophrenia and bipolar disorder after a substance-induced psychosis and risk factors for conversion, researchers analyzed patient information from the Danish Civil Registration System and the Psychiatric Central Research Register for all individuals who were diagnosed with substance-induced psychosis between 1994 and 2014 (n = 6,788). Participants were followed until first occurrence of schizophrenia or bipolar disorder, death or August 2014.

Overall, 32.2% of participants with substance-induced psychosis converted to bipolar or schizophrenia-spectrum disorders.

Participants with cannabis-induced psychosis had the highest conversion rate, with 47.4% (95% CI, 42.7-52.3) converting to schizophrenia or bipolar disorder.

Young age was associated with a higher risk for converting to schizophrenia.

Self-harm after substance-induced psychosis was significantly associated with higher risk for converting to schizophrenia and bipolar disorder.

Approximately half of participants who converted to schizophrenia did so within 3.1 years after substance-induced psychosis, and half who converted to bipolar disorder did so within 4.4 years.

“Based on the different risk factors identified in different analyses and the overall conversion rate of 32.2%, it seems most reasonable to suggest that all patients with a substance-induced psychosis should be offered follow-up,” the researchers wrote. “Our findings suggest that patients who present with self-harm and have previously had a substance-induced psychosis are at even higher risk of converting to schizophrenia or bipolar disorder. In Denmark patients are offered follow-up after self-harm, but not after a substance-induced psychosis.” – by Amanda Oldt

Disclosures: Starzer reports receiving a pregraduate research grant from the Lundbeck Foundation to perform the work reported here. Please see the study for all other authors’ relevant financial disclosures.