Cannabis Use and Mental Health Problems Are Growing Together in Canada - and the Link Is Strengthening

Two trends have been moving in the same direction in Canada over the past decade. Cannabis use has risen substantially - the share of Canadians reporting use in the past year reached 20.7% by 2022, up from lower rates at the start of the study period. At the same time, rates of generalized anxiety disorder and major depressive episodes have nearly doubled. Suicidality increased by 44% among young people.

A study from McMaster University, published in The Canadian Journal of Psychiatry on February 25, 2026, examines these parallel trends across a nationally representative sample of 35,000 Canadians and finds not just that they're occurring simultaneously, but that the relationship between them has grown stronger over time.

What the Data Show

The analysis drew on two large Statistics Canada surveys of Canadians aged 15 and older living in the provinces, covering 2012 to 2022. Canada legalized cannabis nationally in October 2018, placing the legalization point squarely in the middle of the study window.

The headline finding: by 2022, Canadians who used cannabis two or more times per week were approximately five times more likely to report generalized anxiety disorder, major depressive episode, or suicidality compared to those who did not use cannabis. That ratio was already elevated in 2012, but it has increased over the decade.

Multiple-times-per-week use more than doubled over the study period. The number of people meeting criteria for generalized anxiety disorder increased to 5.2%, and for major depressive episode to 7.6%. Youth showed some of the strongest cannabis-mental health connections, and suicidality among younger Canadians specifically rose 44%.

"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 at McMaster's School of Nursing and youth substance use research lead at the Peter Boris Centre for Addictions Research.

What This Study Cannot Establish

The authors are explicit: this is a correlational study, and correlation does not establish causation. It is equally plausible that people experiencing anxiety and depression turn to cannabis to manage symptoms - a self-medication pattern well documented in addiction research - as it is that cannabis use drives mental health deterioration. The most likely reality involves both directions influencing each other.

The study also cannot determine which specific aspect of increased cannabis use - higher THC concentrations in legal products, greater frequency of use, changes in user demographics, or broader cultural acceptance reducing stigma-related barriers to use - best explains the strengthening association. Canada's legal market shifted the composition of available products significantly after 2018, with higher-potency options more widely accessible, but the survey data cannot isolate that variable.

This extends an earlier McMaster study that found a similar strengthening of the cannabis-mental health co-occurrence between 2002 and 2012, suggesting the pattern predates legalization and may reflect longer-running changes in use patterns, product potency, or population vulnerability.

Clinical and Policy Implications

The researchers argue that the growing overlap between cannabis use and mental health problems has concrete clinical consequences. Mental health providers who do not routinely screen for cannabis use may miss a relevant factor in patient presentations. Addiction treatment providers who do not address co-occurring anxiety and depression may see poorer outcomes. The study calls for integrated approaches that treat both substance use and mental health together.

The authors also call for updating Canada's Lower Risk Cannabis Use Guidelines to reflect these strengthened associations, and for earlier detection of anxiety, depression, and suicidality among people who use cannabis - particularly youth.

"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," Halladay said. "It's also increasingly important for health and mental health providers to assess and address both cannabis use and mental health concerns together."