A major Canadian study has revealed a strengthening link between cannabis use and mental health challenges, including anxiety, depression, and suicidal thoughts, particularly among young people. The research, conducted by McMaster University and published in the Canadian Journal of Psychiatry, analyzed data from over 35,000 Canadians collected between 2012, and 2022.
Researchers found that the number of Canadians reporting generalized anxiety disorder and major depressive episodes nearly doubled over the study period, rising to 5.2 percent and 7.6 percent respectively. While adult suicidality rates remained relatively stable, youth suicidality increased by 44 percent. Concurrently, cannabis use also climbed, with the number of individuals using cannabis multiple times a week more than doubling and overall annual cannabis use reaching 20.7 percent.
The study indicated that in 2022, Canadians who used cannabis regularly – defined as two or more times per week – were approximately five times more likely to report symptoms of anxiety, depression, or suicidal ideation compared to those who did not use cannabis. This association has turn into more pronounced over time, coinciding with the legalization of cannabis in Canada in 2018.
Jillian Halladay, an assistant professor at McMaster University and researcher at the Peter Boris Centre for Addictions Research, explained the findings. “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,” she said. “We also see that this co-occurrence has strengthened over time.” Halladay noted that the study builds upon previous research showing a similar trend between 2002 and 2012.
The increasing potency of cannabis products available since legalization is also a factor. Modern cannabis often contains significantly higher levels of THC, the psychoactive compound, than products available in the past. This is particularly concerning for adolescents and young adults, whose brains are still developing and may be more vulnerable to the effects of cannabis.
Researchers emphasize that the study does not establish a causal relationship between cannabis use and mental health disorders, but the strengthening correlation raises significant public health concerns. Adolescence and young adulthood are critical periods for mental health development, and cannabis use can disrupt the brain’s endocannabinoid system, which regulates mood, stress, and memory.
The McMaster University team recommends updating Canada’s Lower Risk Cannabis Use Guidelines to reflect the strengthening associations found in the data. They also call for routine screening for cannabis use in mental health settings and improved access to integrated substance use and mental health services. “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,” the authors wrote in their published study.
The researchers are advocating for health and mental health providers to routinely assess and address both cannabis use and mental health concerns concurrently.
