Question: Is there an association of the increase in cannabis minimum legal age (MLA) from 18 to 21 years in Quebec, Canada, with youth cannabis use?

Findings: In this cross-sectional study with difference-in-differences analysis of 1005 youths aged 15 to 20 years, although youth cannabis use still increased after the policy change, the increase in past-3-month cannabis use among youths aged 18 to 20 years was 51% lower in Quebec than in other provinces. There was no change in cannabis use among youths aged 15 to 17 years.

Meaning: The lower increase in cannabis use among individuals aged 18 to 20 years alleviates concerns that youths would switch to illegal markets in response to a higher MLA; however, the increase in youth cannabis use despite the higher MLA highlights the need for additional policy measures to address rising youth cannabis use.