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Marijuana Legalization in Canada Did Not Result in Increased Use Among High Risk Young Adults



The legalization of recreational cannabis in Canada was met with concerns about potential increases in cannabis use, particularly among young adults who already have a higher prevalence of consumption. The worry was that easier access, social acceptability, lower prices, and a variety of cannabis products could lead to a surge in usage among this demographic. However, a recent longitudinal cohort study sheds light on the actual impact of legalization on cannabis use and its consequences among high-risk young adults in Ontario, Canada.

Details of the Study

This longitudinal observational cohort study followed young adults between the ages of 19.5 and 23.0 in Ontario, Canada, who reported regular heavy episodic drinking (high risk of drug abuse) and fluency in English. The study aimed to assess changes in cannabis use frequency and related consequences over the course of cannabis legalization in Canada. Participants were surveyed every four months for three years, starting in February 2017 and ending in February 2020. The data analysis focused on changes in cannabis use patterns, considering sex, income, education, and pre-legalization cannabis use frequency as potential moderators.

Key Findings

The study yielded several important findings:

  • Overall Decrease in Cannabis Use: In a cohort of 619 high-risk young adults, there was an average decrease in both cannabis use frequency and cannabis-related consequences over time, encompassing the period before and after cannabis legalization in Canada.
  • Moderated Changes: The changes observed in cannabis use frequency and consequences were significantly moderated by pre-legalization cannabis use frequency. This means that the patterns of change differed depending on whether individuals were frequent users before legalization or not.
  • Frequent Users Decreased Their Consumption: Individuals who used cannabis frequently before legalization showed significant reductions in both cannabis use and related consequences after legalization. This pattern aligns with what researchers refer to as “aging out,” where individuals naturally reduce their substance use over time.
  • Occasional Users Increased Slightly: In contrast, individuals who did not use cannabis before legalization exhibited a small increase in cannabis use frequency over time, but there were no significant changes in cannabis-related consequences. This suggests that the increase in usage was modest and not accompanied by a proportional rise in negative consequences.
  • Moderators of Change: Sex, income, and education did not significantly moderate the changes in cannabis use patterns over time, indicating that these changes were relatively consistent across different demographic groups.


Contrary to concerns that cannabis legalization in Canada would lead to a surge in cannabis use, particularly among young adults, this study suggests otherwise. High-risk young adults, who are more prone to substance use, showed different patterns of change in cannabis use frequency and consequences. Frequent cannabis users before legalization experienced reductions in use and related consequences, likely reflecting a natural aging-out process. On the other hand, individuals who were not cannabis users before legalization saw only a modest increase in usage, with no substantial increase in related consequences.

These findings offer valuable insights into the real-world impact of cannabis legalization on youth and young adults. While the study does not rule out the possibility of alternative trajectories in the absence of legalization, it highlights that legalization alone did not result in significant adverse near-term outcomes among the studied population. Nonetheless, ongoing research and monitoring are essential to comprehensively assess the long-term effects of cannabis legalization on public health, particularly among young adults.


Lydia K. (Bsc. RN) is a cannabis writer, which, considering where you’re reading this, makes perfect sense. Currently, she is a regular writer for Mace Media. In the past, she has written for MyBud, RX Leaf & Dine Magazine (Canada), CBDShopy (UK) and Cannavalate & Pharmadiol (Australia). She is best known for writing epic news articles and medical pieces. Occasionally, she deviates from news and science and creates humorous articles. And boy doesn't she love that! She equally enjoys ice cream, as should all right-thinking people.