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Cannabis' link to psychotic disorders in teens is stronger than previously believed

Cannabis legalization has been a hot topic, with proponents touting its potential medical benefits and opponents raising alarms about potential health risks, particularly with teens.

Now, a new study is reigniting the debate, suggesting a stronger link than previously thought between teen cannabis use and the development of psychotic disorders.

What does this mean for teens, parents, and policymakers?

Teens using cannabis

Researchers from the University of Toronto, the Centre for Addiction and Mental Health (CAMH), and the Institute for Clinical Evaluative Sciences (ICES) embarked on a comprehensive study involving over 11,000 young people in Ontario, Canada.

By linking self-reported cannabis use with health records, they uncovered a startling trend: teens who use cannabis are 11 times more likely to develop a psychotic disorder than those who don’t.

According to healthcare professionals, this is a wake-up call, especially considering the rising potency of cannabis products.

“These findings are consistent with the neurodevelopmental theory that teens are especially vulnerable to the effects of cannabis,” lead author André McDonald notes.

Teens are more vulnerable to cannabis impacts

One of the most striking aspects of the study is the age-dependent nature of the association. Teens who used cannabis faced a significantly elevated risk of psychosis, while young adults did not show the same link.

This suggests a critical window of vulnerability during adolescence, a period when the brain undergoes significant changes. The findings highlight the importance of focusing prevention efforts on younger individuals, as their developing brains may be more susceptible to the effects of cannabis.

Understanding this age-specific risk is crucial for developing effective public health strategies to mitigate the potential harms of cannabis use.

“We found a very strong association between cannabis use and risk of psychotic disorder in adolescence. Surprisingly, we didn’t find evidence of association in young adulthood,” says McDonald.

This age-specific risk underscores the importance of targeted prevention strategies for teens.

Impact of cannabis use on teens

The study’s findings are sobering. Roughly 5 out of 6 teens hospitalized or visiting the emergency department for a psychotic disorder had previously reported using cannabis.

The average THC potency of cannabis in Canada has skyrocketed from 1% in 1980 to 20% in 2018. While most teens who use cannabis won’t develop a psychotic disorder, most teens diagnosed with a psychotic disorder have a history of cannabis use.

This further highlights the significant risk associated with cannabis use during adolescence, emphasizing the need for prevention and awareness efforts to protect young people’s mental health.

These figures paint a complex picture. While cannabis use doesn’t guarantee a psychotic disorder, the strong correlation raises serious concerns about the potential consequences, especially for young people.

Need for prevention and further research

The researchers acknowledge the study’s limitations, including the possibility of reverse causation, where teens with psychotic symptoms may self-medicate with cannabis, and the lack of data on genetic and environmental factors.

Despite these limitations, the findings highlight the urgent need for more research and proactive prevention strategies. The strong association between teen cannabis use and psychotic disorders calls for increased awareness and targeted interventions to protect adolescent mental health.

Understanding the broader impacts and underlying causes will be crucial for developing effective public health policies and minimizing the risks associated with early cannabis use.

“As commercialized cannabis products have become more widely available, and have a higher THC content, the development of prevention strategies targeting teens is more important than ever,” notes senior author Susan Bondy.

Study implications

Whether you’re a parent, a teen, or someone interested in public health, these findings are relevant. They highlight the importance of several things:

Open conversations

Talking to your teens about the potential risks of cannabis use is crucial, especially during adolescence. Engage in open and honest discussions about how cannabis can affect their developing brain and mental health.

Create a safe space where they feel comfortable asking questions and expressing their thoughts. Highlight the increased risks and share the latest research findings to provide a clear understanding of why avoiding cannabis is important during their formative years.


Stay informed about the latest research on cannabis and its effects on the brain. Knowledge is power, and by keeping up-to-date with new studies and findings, you can provide accurate information to your teens.

Understanding the changes in cannabis potency and the specific risks associated with adolescent use can help you make informed decisions and guide your children effectively.

Attend community talks, read scientific articles, and utilize resources from reputable health organizations to stay educated.


Support initiatives that aim to reduce teen cannabis use and promote healthy alternatives. Get involved in local and national campaigns focused on preventing early cannabis use. Advocate for policies that restrict the availability of high-potency cannabis products to minors.

Encourage schools and community programs to incorporate cannabis education into their curricula. Additionally, promote and participate in activities that offer healthy and engaging alternatives to drug use, such as sports, arts, and volunteer opportunities.

The debate over cannabis legalization is far from over. But with this new evidence, it’s clear that we need to prioritize the health and well-being of young people, protecting them from potential harm while exploring the potential benefits of this complex plant.

The study is published in the journal Psychological Medicine.


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