Cannabis Use Frequency and Cannabis-Related Consequences in High-Risk Young Adults Across Cannabis Legalization

Abstract

Importance: A key concern about recreational cannabis legalization is increases in use and adverse consequences, particularly among young adults (aged 18-29 years) who have the highest prevalence of cannabis use, and especially in higher-risk, more vulnerable young adults. However, few longitudinal studies have examined patterns of cannabis consumption in high-risk young adults over the course of legalization. Objective: To examine changes in cannabis use frequency and cannabis-related consequences over recreational cannabis legalization in Canada in a longitudinal sample of high-risk young adults. Design, Setting, and Participants: Longitudinal observational cohort study following young adults in Ontario, Canada, aged 19.5 to 23.0 years who reported regular heavy episodic drinking (65% past-month cannabis use) at enrollment. Participants were surveyed every 4 months for 3 years between February 2017 and February 2020 (3 prelegalization waves, 4 postlegalization waves). Data were analyzed from March to May 2023. Exposures: Recreational cannabis legalization in Canada and 4 potential moderators of change: sex, income, education, and prelegalization cannabis use frequency. Main Outcomes and Measures: Cannabis use frequency and cannabis-related adverse consequences. Results: In a cohort of 619 high-risk young adults (baseline mean [SD] age, 21.0 [1.2] years; 346 female participants [55.9%]), omnibus model testing revealed significant overall decreases in both cannabis use frequency (F = 2.276, 3000.96; P =.03) and cannabis-related consequences (F = 10.436, 3002.21; P