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Legalization not linked to upticks in cannabis-induced psychosis

Published on March 7, 2024 by Special to the oz.

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Legalization in Canada is not associated with increases in cannabis-induced psychosis, according to data published in The Canadian Journal of Psychiatry.

Canadian researchers assessed the frequency of cannabis-related psychotic incidents requiring hospitalization in the 12 months preceding legalization and in the 12 months following its enactment.

Scientists reported “no increase in the proportion of ED [emergency department] consultations for a psychotic episode in which evidence for cannabis consumption was obtained before and after legalization.” They acknowledge that their findings were “in line with previous studies stating that legalization had no significant impact on ED’s consultations for psychosis.”

Two other Canadian studies have reached similar conclusions. The first, published in 2022, determined, “[The] implementation of Canada’s cannabis legalization framework was not associated with evidence of significant changes in cannabis-induced psychosis or schizophrenia ED presentations.” The second, published earlier this year, “did not find evidence of increases in health service use or incident cases of psychotic disorders over the short-term (17 month) period following cannabis legalization.”

In the United States, state-level marijuana legalization laws have not been associated with a statistically significant increase in psychosis-related health outcomes. Specifically, a 2022 paper published in the Journal of the American Medical Association (JAMA) Network Open found no association between the adoption of marijuana legalization and overall rates of psychosis-related diagnoses or prescribed antipsychotics.

Although the use of cannabis and other controlled substances tends to be more common among those with psychotic illnesses, lifetime incidences of marijuana-induced psychosis are relatively rare among those who do not have a prior psychiatric diagnosis. According to one recent study, fewer than one-half of one percent of cannabis consumers had ever reported experiencing psychotic symptoms requiring medical intervention – a percentage that is lower than the rate associated with alcohol.

Full text of the study, “Effect of cannabis legalization in Canada on the incidence of psychosis consultations in Quebec City’s psychiatric emergency services,” appears inThe Canadian Journal of Psychiatry.

— Norml