One hallmark of Justin Trudeau’s leadership in Canada was legalizing cannabis, making it legal to buy it at shops and dispensaries even without a doctor’s note. That act has made accessibility to cannabis commonplace and within reach for teens too, who are fond of gummies and edibles. But cannabis can hurt developing brains, and it’s not only providing pain relief and therapy. While it can calm symptoms of PTSD, it can also lead to negative outcomes such as anxiety and depression, finds a new study.
The study looked at 35,000 Canadians who use cannabis and shows that rising cannabis use and worsening mental-health symptoms are increasingly appearing together, with the connection between the two strengthening over time.
The study, led by McMaster University, was published in The Canadian Journal of Psychiatry and analyzed data from two large, nationally representative Statistics Canada surveys of Canadians aged 15 and older living in the provinces, to examine cannabis use and mental-health outcomes between 2012 and 2022.
With the legalization of cannabis in Canada landing at the midpoint of the study period, the authors suggest that stronger products, wider availability, and increased use for stress relief may be contributing to the patterns they observed. The study doesn’t prove causation, but it underscores a widening public-health issue as cannabis use and mental-health challenges rise in parallel.
“We see that Canadians who use cannabis tend to be more likely to meet criteria for anxiety and depressive disorders, and more likely to report suicidality. We also see that this co-occurrence has strengthened over time,” said Jillian Halladay, an assistant professor who contributed to the study.
Key findings:
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The number of people reporting generalized anxiety disorder and major depressive episode nearly doubled, increasing to 5.2% and 7.6%, respectively.
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Suicidality didn’t change much in adults but increased by 44% among youth. Younger Canadians also saw some of the strongest cannabis–mental-health connections.
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Canadians who used cannabis at any level, compared to those who did not, were more likely to meet criteria for generalized anxiety disorder and major depressive episode and report suicidality. The connection between cannabis use and these mental-health problems strengthened over time.
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In 2022, Canadians who used cannabis regularly (two or more times a week) were about five times more likely to report anxiety, depression, or suicidality than those who did not use cannabis.
“This extends our prior study that similarly found a strengthening in the co-occurrence of cannabis use and these mental-health problems between 2002 and 2012,” she says.
Halladay and her fellow researchers emphasize that the growing overlap between cannabis use and mental-health problems highlights the need for earlier detection of anxiety, depression, and suicidality among people who use cannabis, as well as routine screening for cannabis use in mental-health settings.
“It’s important for people to recognize when and how their cannabis use may be impacting their mental health, and how their mental health may be influencing their cannabis use. It’s also increasingly important for health and mental-health providers to assess and address both cannabis use and mental-health concerns together.”
This study furthers recent research from McMaster that found anxiety and depression rates among teenagers increased nearly three-fold over the last decade. In that study, rates of anxiety and depression were higher in teens who use cannabis heavily.
