Mental health challenges among teenagers in Ontario are rising at an alarming rate, and new research suggests cannabis use may be increasingly tied to that trend.

A recent study from McMaster University found that psychological distress among teens has nearly tripled over the past decade. While many factors are likely contributing to this shift, researchers say frequent cannabis use is becoming a more significant part of the picture, raising new concerns for families, educators, and policymakers already grappling with growing mental health needs.

A Decade of Change

The study, published in the journal Addiction in January 2026, analyzed data from over 35,000 students in grades 7 through 12 across Ontario.

The findings point to a dramatic increase in reported mental health struggles:

  • Rates of depression and anxiety rose from 10.7% in 2013 to 27.4% in 2023
  • About 20% of students reported using cannabis.
  • Roughly 4% reported frequent use (40 or more times per year)

Perhaps most notably, teens who used cannabis frequently reported significantly higher levels of psychological distress, an 18% increase compared to non-users in 2023. A decade earlier, that gap was virtually nonexistent.

“Far more Ontario teens are reporting mental health problems than a decade ago, and frequent cannabis use is increasingly part of that story,” said lead author André McDonald.

Today’s cannabis products are also more potent than in the past, which may increase potential risks, especially for adolescents whose brains are still developing.

Still, experts caution that the relationship is not entirely clear-cut.

Teens and Cannabis: Understanding the Risks

The teen years are a period of growth, exploration, and taking risks. Some risks, like running for student council or asking someone on a date, can support identity development and independence. However, certain behaviours, such as cannabis use, can negatively affect a teen’s health and well-being.

The adolescent brain continues developing into the mid-20s, and cannabis use during this time can interfere with brain development. Teens who use cannabis are more likely to struggle academically, including being at higher risk of not finishing high school or attending college, compared with peers who do not use cannabis.

Negative Effects of Teen Cannabis Use

Cannabis use can lead to:

  • Difficulty thinking clearly and solving problems
  • Memory and learning challenges
  • Reduced coordination
  • Trouble focusing
  • Struggles in school and social relationships

How Cannabis Can Affect a Teen’s Life

  • Mental Health Risks: Cannabis is linked to increased risk of depression, social anxiety, and temporary psychosis (hallucinations, paranoia, confusion). Early and frequent use can increase the likelihood of long-term mental disorders, including schizophrenia.
  • Impaired Driving: Cannabis affects reaction time, coordination, and concentration, making driving unsafe and illegal while impaired.
  • Potential for Addiction: About 3 in 10 cannabis users develop cannabis use disorder. Signs include difficulty quitting and prioritizing cannabis over important activities. Youth who start early or use frequently are at higher risk.

Why Teens Use Cannabis

In 2023, nearly half of teens who used cannabis said it was a way to cope with mental health challenges, often because their needs were not fully met. Researchers note a complex relationship: cannabis can worsen mental health, but teens may also turn to it because they are already struggling.

A Stronger Impact on Girls

Research shows that girls often experience a stronger link between cannabis use and psychological distress. Girls report higher levels of anxiety and depression overall, which may reflect social and emotional pressures as well as differences in how mental health challenges are experienced and reported.

Broader Context

Cannabis is only one factor in rising teen distress. Other challenges include:

  • Lasting impacts of the COVID-19 pandemic
  • Economic uncertainty
  • Increased social and academic pressures

Similar trends in youth mental health have been observed in other high-income countries, pointing to a global shift.

What Can Help

Experts suggest strategies to support teen mental health and reduce cannabis-related risks:

  • Delay the start of cannabis use.
  • Reduce the frequency of use.
  • Avoid high-potency products.
  • Improve access to mental health support, particularly for teens using substances to cope.

At the same time, improving access to mental health support remains critical, particularly for young people who may be using substances as a form of self-medication. Understanding how and why teens are coping, whether through substances or other means, will be key to addressing the growing mental health crisis.

Because behind the statistics are real young people trying to manage challenges that, for many, are becoming harder to carry.

Resources

If you or someone you know is struggling with mental health, cannabis use, or both, here are some Canadian support options:

Call or text 9‑8‑8 (Canada suicide prevention and mental health support line) – available 24/7.