Opponents of cannabis legalization often claim that marijuana can increase the risk of suicide. But a new study suggests that the alleged link between cannabis and suicide is baseless.

Yes, there is a high rate of cannabis use among people who suffer from mental health issues. And those statistics have led people to blame depression, severe anxiety and other psychological issues on excessive cannabis use. But the actual relationship between psychiatric disorders and cannabis use have not been properly explored until researchers from McMaster University began investigating the alleged connection.

"[T]his 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 lead author Zainab Samaan, an associate professor in the Department of Psychiatry and Behavioural Neurosciences at McMaster. "We know there is a high rate of cannabis use among this population and wanted to better understand any potential correlation to suicidal behavior."

The study analyzed data collected from 909 participants with nearly an even split between men and women. Close to 35 percent of the people studied had previously attempted suicide. Co-author Leen Naji says the study found "no clear link between cannabis and suicide attempts."

However, there is one caveat. Extremely heavy cannabis use among men does seem to correlate with an increased risk of suicide. In light of this Naji says there is still more work to be done before scientists can conclude whether that finding is causative or merely coincidental. 

"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."

But researchers did find three factors that do increase the risk of 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," Naji added.

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