Psychological distress among teenagers more than doubled in the last decade in Ontario, Canada, and cannabis use is statistically associated with this scenario — especially among female youth and those who consume the substance more frequently. This is revealed by a population study published in January 2026 in the scientific journal Addiction.

The research analyzed data from 35,007 elementary and high school students, from 7th to 12th grade, collected between 2013 and 2023 through the Ontario Student Drug Use and Health Survey. The results show that while cannabis use among teenagers decreased during the period, indicators of anxiety and depression grew significantly.

Psychological distress increases despite decrease in cannabis use

According to the survey, the prevalence of psychological distress — measured by the Kessler-6 scale, which assesses symptoms of anxiety and depression — rose from 10.7% in 2013 to 27.4% in 2023. In the same interval, cannabis use in the last year dropped from 23.1% to 17.6% among teenagers.

Despite the reduction in the number of users, the study identified that young people who consumed cannabis had a higher prevalence of psychological distress compared to non-users, even after adjustments for age, socioeconomic status, alcohol, and cigarette use.

Among teenagers who reported very frequent use — 40 times or more in the year — the association strengthened over time. In 2013, there was no statistically significant difference compared to non-users. In 2023, this group showed a psychological distress prevalence 18 percentage points higher.

Differences between genders and impact of frequency of use

One of the key findings of the study is the marked difference between genders. Among girls, cannabis use showed a clear dose-response relationship: the higher the frequency of consumption, the higher the prevalence of psychological distress. Among boys, this association was not statistically significant in any of the analyzed usage categories.

According to the data, girls who used cannabis 40 times or more in the last year had a psychological distress prevalence 19% higher than those who did not use the substance. The pattern persisted even after controlling for behavioral and socioeconomic factors.

The authors also observed that earlier onset of cannabis use is associated with worse mental health outcomes. Each additional year of delay in the onset of consumption was associated with a 5% reduction in the prevalence of psychological distress among high school students.

THC potency and use as a coping strategy

Although the study did not directly measure the potency of the cannabis products consumed, researchers used the year of the study as an indirect indicator of the increase in THC content over time. Canadian data shows that the average THC concentration in cannabis increased from about 6% in the 1990s to approximately 20% from 2018 onwards, in addition to the popularization of extracts with even higher concentrations.

In 2023, nearly half of the teenagers who used cannabis stated they consumed the substance as a way to cope with psychological distress. Among girls with very frequent use, this percentage reached 96%. The study also identified high levels of unmet mental health care needs, especially among frequent users.

The authors emphasize that, despite the observed association, the cross-sectional design of the study does not allow for establishing causality. Nevertheless, the results raise relevant concerns for youth public health.

Implications for public policies

Based on the precautionary principle, researchers argue that prevention strategies should prioritize reducing frequency of use, delaying the age of initiation, and controlling the potency of cannabis products, with special attention to female adolescents.

The study reinforces the need to integrate mental health and substance use prevention policies in a context of increased access, social normalization of cannabis, and consistent rise in psychological distress indicators among youth.