Study: Marijuana Use Not Associated With Increased Risk of Psychosis

According to a new study published in the journal Psychiatry and Clinical Neurosciences a history of marijuana use is not associated with an increased risk of developing psychosis, even among those predisposed to the disorder.

The primary aim of the study “was to examine the association between cannabis use and the incidence of psychotic disorders in people at clinical high risk of psychosis.” Secondary aims were to assess “associations between cannabis use and the persistence of psychotic symptoms, and with functional outcome.”

In doing so, researchers found that “There was no significant association between any measure of cannabis use at baseline and either transition to psychosis, the persistence of symptoms, or functional outcomes.”

For the study current and previous cannabis use were assessed in individuals at clinical high risk of psychosis (334) and healthy controls (67), using a modified version of the Cannabis Experience Questionnaire. Participants were assessed at baseline and followed up for 2 years, and transition to psychosis and persistence of psychotic symptoms were assessed using the Comprehensive Assessment of At-Risk Mental States criteria. Level of functioning at follow up was assessed using the Global Assessment of Functioning disability scale.”


During follow up, 16.2% of the clinical high-risk sample developed psychosis. Of those who did not become psychotic, 51.4% had persistent symptoms and 48.6% were in remission. Researchers report that there “was no significant association between any measure of cannabis use at baseline and either transition to psychosis, the persistence of symptoms, or functional outcome.”

Researchers conclude:

These findings contrast with epidemiological data that suggest that cannabis use increases the risk of psychotic disorder. This article is protected by copyright. All rights reserved.

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