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Résumé (français)

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Résumé (anglais)

Purpose As recreational cannabis is legalized, it is critical to know the impacts of legalization on youth cannabis use. Existing research generates conflicting results and does not shed light on channels of effects. This study investigates the impacts of legalization on youth cannabis initiation and overall cannabis use prevalence. Methods We used Interrupted Time Series design and data from nationally-representative repeated cross-sectional Canadian surveys spanning 16 years. The primary outcomes were cannabis initiation rates and cannabis use prevalence among youths. The secondary outcomes were self-reported age of first cannabis use, ease of cannabis access, and perception of cannabis harm among youths. Results After legalization, cannabis initiation rate among youths was 2.7 percentage points (95% confidence interval: 1.7–3.7; p < .01) or 69% higher, although there was no significant increase in the overall prevalence of cannabis use. Furthermore, there was a 4-month delay in the average age of first cannabis use among youths aged 17–18 years (95% confidence interval: 2.6–5.5 months; p < .01). The legalization was associated with greater perception of cannabis harm but also easier access to cannabis. Discussion The impacts of legalization on youth cannabis use after 1 year are mixed. Although we observed an increase in cannabis initiation among youths who had never used cannabis, there was no change in the overall prevalence of cannabis use, implying a possible offsetting increase in cannabis cessation among existing users. To achieve legalization's goal of reducing youth cannabis use, policy measures are needed to curb youth cannabis access and initiation.