Clearing the Air About Cannabis: Trends in Student Cannabis Use Since Legalization |

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Clearing the Air About Cannabis: Trends in Student Cannabis Use Since Legalization

Friday, September 4, 2020 - 10:41

In the period surrounding cannabis legalization in Canada, questions abounded on the impact it would have on youth. As an educator, you may have debated with your colleagues, or had friends and family members asking your opinion. Today, we finally have data to help us understand what’s changed and what hasn’t since cannabis was legalized in October 2018.

The Ontario Student Drug Use and Health Survey – OSDUHS (“oz-duss”) for short – is the longest ongoing surveillance program of mental health, substance use and wellbeing among students in grades 7 to 12 in Ontario’s publicly funded schools. In order to understand the trends since legalization, we will be looking at OSDUHS results from 2017, before legalization, and comparing them to the most recent 2019 survey. We’ll also take a look at some national data to see how Ontario compares to the Canadian average.

For a summary of the key cannabis-related OSDUHS results, check out this infographic.

Are students using cannabis more since legalization?

Overall, students in grades 7-12 are NOT using cannabis more since legalization. In 2017, 19% of students in grades 7-12 reported using cannabis in the past year. In 2019, this figure was 22%1. Although this looks like a higher percentage, the increase is not statistically significant. Similarly, the Canadian Student Tobacco, Alcohol and Drugs Survey found no significant increase since legalization2.

When we look at each grade individually, the OSDUHS found that only grade 8 students had a significant increase in cannabis use since legalization (2% in 2017 to 5% in 2019)1. However, researchers believe this is likely just a blip, as the level is in line with previous years. National data reveals that Canadian students in grades 7-9 reported an increase from 6% in 2016-17 to 7% in 2018-19. However, cannabis use among Canadian students in grades 10-12 remained unchanged at 29%2.

It is also important to consider the substance use continuum. A student who used cannabis once over the past year would likely fall in a different segment of the continuum from another student who used cannabis every day. The OSDUHS data shows that the percentage of students in grades 9-12 who use cannabis daily has doubled since legalization (i.e. 1% in 2017 to 2% in 2019)1.

Since students may be reticent to disclose their own substance use, it can be helpful to consider students’ perspectives on their peers’ use. When high school students were asked about their friends’ use of cannabis since legalization, 27% said it did not change, 14% said it increased, and 22% were not sure1. Similarly, when asked if it has been easier to obtain cannabis since legalization, 4% of Canadian students said it has been easier, less than 1% said it has been harder, and 12% said it is neither easier nor harder. The remaining 83% never tried to buy or obtain cannabis2.

How are students consuming cannabis since legalization?

Students may be using cannabis in a number of different ways including joints, pipes or bongs, edibles (food), e-cigarettes or vapes, among others. While joints remain the most common method (21%), followed by pipes/bongs (19%), edibles have seen a significant increase since legalization, rising from 11% in 2017 to 14% in 20191. National data also shows an increase in the use of edibles, as well as increased vaping and dabbing2. The percentage of Canadian students who use more than one method has not changed since pre-legalization2.

“It will be important to continue to monitor cannabis use over time. Our study was conducted not long after legalization and, therefore, an examination of longer term impacts are needed. New policy changes such as the introduction of cannabis edibles have also been implemented since our last survey and we will need to examine whether this policy change has impacted cannabis use.” – Dr. Tara Elton-Marshall, Independent Scientist and co-author of the OSDUHS

For more on edibles and the specific risks related to this method of consumption, check out last year’s Q&A Column, Clearing the Air on Cannabis: Edibles.

For more detailed information on methods of cannabis consumption, check out this report from the Canadian Centre on Substance Use and Addiction.

How can I use this data to support my students?

“There has been a decline in students' perceived risks of using cannabis, either experimentally or regularly, over the past decade or so. There is, therefore, a need to educate students about the short and long-term effects of cannabis use and the different health effects of different modes of using cannabis (e.g., smoking cannabis has negative respiratory health effects, consuming cannabis edibles can lead to overdosing). Students need to be made aware that just because cannabis is legalized doesn't mean that it is harmless.” – Dr. Tara Elton-Marshall, Independent Scientist and co-author of the OSDUHS

As educators, our role is not to control students’ behaviours, but rather to empower them to make informed choices about their health and well-being. Teachers play an important role in providing relevant, age-appropriate learning experiences for their students, informing parents/guardians/caregivers about their child’s learning, and promoting a school-wide approach to cannabis education. With that in mind, two key ways to support your students are by providing age-appropriate content and having open conversations.

Age-Appropriate Content

It is helpful to remember that the majority of students are not using cannabis, but the prevalence varies by grade. For grade 7-8 teachers, between 1-5% of your students may use cannabis. In grades 9-10, this number rises to 13-22%. In grades 11-12, up to 40% of students may use cannabis1. Furthermore, recent research shows that few students decrease their cannabis use grade by grade, but those who quit tend to achieve higher math marks than those who continue to use3.

These statistics show how crucial it is to provide timely educational intervention. Cannabis education begins explicitly in Grade 5 in the Healthy Living strand of the Health and Physical Education curriculum. If you teach grades 5 and up, use our curriculum-linked Activity Plans to engage students in inquiry-based activities around cannabis. If you teach, grades 1 to 4, follow the Ontario Curriculum, Grades 1-8: Health and Physical Education 2019 to prepare students for learning about cannabis, by covering expectations related to prescription and non-prescription medication, legal and illegal substances, and smoking and vaping.

Open Conversations

No matter what grade you teach, it’s important to engage in conversations about substance use, addictions, and related behaviours, not only with students, but also with other teachers and parents/guardians/caregivers. These open conversations supplement your teaching practice, and help equip students with the ability to make informed decisions about their health. For example, you may help students assess the health harms compared to the perceived benefits of substance use.

Recognize that substance use, addictions, and related behaviours may be sensitive topics for discussion. It’s best to approach conversations about non-medical cannabis in a knowledgeable, supportive, and non-judgmental way, and to respect the diverse perspectives you may encounter. For example, consider having students complete an anonymous survey in order to gather information about the class profile and their understanding of non-medical cannabis. Consider leaving more space for youth voice by having students brainstorm ways they can make healthy decisions or take healthful action.

Our discussion guides, Cannabis Education: Activate the Discussion (elementary & secondary), can help facilitate open conversations. The guides include practical tips to consider before leading cannabis-related conversations with students, other teachers, and parents/guardians/caregivers. They also provide targeted questions and prompts. If you’re new to these conversations, start by reading the info sheet Cannabis: What Educators Need to Know.

Learn More

For more on this topic, check out the following resources:

To access our full selection of Cannabis Education Resources visit: (Aussi disponible en français: Ressources d’éducation sur le cannabis).

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Ophea and the Provincial System Support Program at CAMH


  1. Boak, A., Elton-Marshall, T., Mann, R. E., & Hamilton, H. A. (2020). Drug use among Ontario students, 1977-2019: Detailed findings from the Ontario Student Drug Use and Health Survey (OSDUHS). Toronto, ON: Centre for Addiction and Mental Health.
  2. Government of Canada. (2019). Canadian Student Tobacco, Alcohol and Drugs Survey. Retrieved from
  3. Zuckermann, A. M., Gohari, M. R., de Groh, M., Jiang, Y., & Leatherdale, S. T. (2020). Cannabis cessation among youth: rates, patterns and academic outcomes in a large prospective cohort of Canadian high school students. Health Promotion & Chronic Disease Prevention in Canada: Research, Policy & Practice, 40(4).