A new Canadian study finds no notable link between cannabis use and suicidal behavior in most people with psychiatric disorders.

The findings, published in the journal Biology of Sex Differences, contrast with previous data suggesting that the drug is associated with an increased risk of suicidal behavior in the general population.

In a small subset of participants, however, heavy cannabis use was linked to a greater risk of suicidal behavior in men, suggesting a closer follow-up by medical professionals among patients in this group.

“In what we believe to be a first, this study seeks to understand how cannabis use impacts suicide attempts in men and women with psychiatric disorders who are already at a heightened risk of attempting suicide,” said Dr. Zainab Samaan, lead author and an associate professor in the Department of Psychiatry and Behavioural Neurosciences at McMaster University.

“We know there is a high rate of cannabis use among this population and wanted to better understand any potential correlation to suicidal behavior.”

Cannabis is the most commonly used illicit substance worldwide, and its consumption is expected to increase as more jurisdictions, including Canada, legalize its use.

For the study, the researchers compared data collected for two studies based in Ontario. These included a prospective cohort study of opioid use disorder using structured scales to determine psychiatric diagnoses, and a case-control study on suicidal behavior using the same diagnostic methods to reach a psychiatric diagnosis including substance use.

The researchers analyzed data from 909 psychiatric patients (average age 40), including 465 men and 444 women. Among this group, 112 men and 158 women had attempted suicide.

“While there was no clear link between cannabis and suicide attempts, our findings did show that among participants with psychiatric disorders, having a mood disorder or being a woman correlates with an increased risk of suicide attempt,” said Dr. Leen Naji, the study’s first author and a family medicine resident at McMaster. “Meanwhile, having a job is protective against suicide attempts.”

Naji said that more research is still needed, considering the changing laws on cannabis use, and the Mental Health Action Plan of the World Health Organization which has the aim to reduce the rate of suicide by 10 percent by 2020.

“Our study is both timely and relevant, especially in light of the impeding legalization of recreational cannabis with an expected increase in access in Canada, and there remains uncertainty about the full effect of cannabis on those living with psychiatric disorders,” she said.

The new findings may serve to educate health professionals when evaluating a patient’s risk of suicide. Samaan said the results also reinforce suggested benefits of supporting patients with psychiatric disorders in job placements and skills development.

Source: McMaster University