Clearing the Air About Cannabis: Brain Development and Related Harms |

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Clearing the Air About Cannabis: Brain Development and Related Harms

Tuesday, March 5, 2019 - 11:14

Following our first Clearing the Air About Cannabis Q&A column featuring a discussion on legalization with Jean‐François Crépault, Senior Policy Analyst at the Centre of Addiction and Mental Health (CAMH), we received questions asking for us to expand on his comments referring to cannabis harms for youth and brain development.

It is important to remember that the majority of youth will not use cannabis – According to the 2017 Ontario Student Drug Use and Health Survey (OSDUHS) 81% of students in grades 7 to 12 reported that they have not used cannabis at all in the past year.1 For most youth, trying cannabis is unlikely to cause serious problems. However, even occasional use can be harmful.

Cannabis use has been associated with increased risk of long-term health and social problems when it begins at a young age, it is frequent, and continues over the long-term (for months or years).2 In 2017, 1.4% students in grades 7 to 12 used cannabis daily in the previous month.1 According to The Effects of Cannabis Use during Adolescence  published by the Canadian Centre on Substance Use and Addiction in 2015, there are key brain development phases during adolescence and that are susceptible to the effect of cannabis.3 Studies of brain development have found that those who started using at an early age have altered brain development, reduced brain volume, and disrupted neural regulation.3

What are the Physical Effects?

Brain development differences have been documented in the prefrontal cortex, associated with executive functioning, the amygdala, associated with emotional regulation, and the cerebellum, associated with psychomotor skills, among others.3 The prefrontal cortex, which governs cognitive functions like planning and decision making, is particularly vulnerable because it is not fully formed and it is undergoing a period of fine tuning in adolescence.3 Changes in the development of the prefrontal cortex can lead to problems with memory, concentration, decision making, learning, impulse control, handling emotions, and problem solving. This in turn can lead to difficulties with completing school work, lower school performance, and increased risk of dropping out of high school.3

What are the Psychological Effects?

Adolescence is also a time of psychological development and a time when symptoms of mental health and problematic substance use can typically emerge. It is not yet clear as to whether substance use can cause mental health concerns, or if there is a shared vulnerability between the two. There is a strong evidence of a link between early cannabis use and mental illnesses. Early cannabis use had been linked to psychosis, and more recently to depression, anxiety, eating disorders and behavioural disorders.3  In addition, cannabis can be especially addictive for youth, and 17% of those who start in adolescence will develop symptoms of dependence. 3

Further research is needed to better understand how the age when youth start using cannabis and the way it is used affects brain development and challenges with mental health and problematic substance use. However, the mounting evidence suggests that youth are at particular risk when they start using cannabis early and use it frequently. 2,3   They are more vulnerable than other populations to cannabis harms because their brains are still developing and the related harms may not be fully reversible when use stops.

So what does this all mean for educators and for students?

It is important that students understand the risks unique to them and the relation of these to their developing brain.   To recap, these risks may include problems with:

  • Memory
  • Concentration
  • Decision making
  • Learning
  • Impulse control
  • Handling emotions
  • Problem solving
  • Completing school work
  • Lower school performance
  • Increased risk of dropping out of high school

Students need to have the best information possible so they can make informed decisions about their safety, health and well‑being.  There is no doubt that educators play a critical role in this.  Providing students with these facts in a safe space such as a classroom can help students critically think about their choices.  Access to knowledge and tools will build confidence and support students in making healthy and well-informed decisions when they are confronted with situations and choices related to cannabis.

To support these important conversations with your students, School Mental Health ASSIST, the Ministry of Education, and the Provincial System Support Program at CAMH have just released a new information sheet to help educators talk to youth about cannabis.

A parents/guardians and caregivers information sheet is also available to support talking to youth about cannabis.  This sheet includes an extensive list of references, which may provide educators with additional resources for deepening their knowledge and understanding of cannabis too.

Visit Ophea’s Clearing the Air About Cannabis Q&A Form to submit your questions for next month’s Q&A column. For access to a database of resources visit Cannabis Education Resources. You can also sign up for Ophea’s e-newsletter eConnection to read the next month’s Q&A column and to stay up-to-date with the latest issues, events, and resources!

Thank you!
Ophea and the Provincial System Support Program at CAMH


  1. Boak, A., Hamilton, H., Adlaf, E. M., & Mann, R. R. (2017). Drug use among Ontario students, 1977-2017: Detailed findings from the Ontario Student Drug Use and Health Survey (OSDUHS) (CAMH Research Document Series No. 46). Retrieved from:  
  2. Government of Canada. Health effects of cannabis. Retrieved from:
  3. George, T., & Vaccarino, F. (Eds.). (2015). Substance abuse in Canada: The Effects of Cannabis Use during Adolescence. Ottawa, ON: Canadian Centre on Substance Use and Addiction. Retrieved from: