Does recreational cannabis legalization change cannabis use patterns? Evidence from secondary school students in Uruguay.

BACKGROUND AND AIMS In 2013, Uruguay became the first country to legalize and regulate the production and distribution of cannabis for recreational use. We measured whether Uruguay's non-commercial model of recreational cannabis legalization was associated with changes in the prevalence of risky and frequent cannabis use among secondary school students. DESIGN We used data from repeated cross-sectional surveys of secondary students in Uruguay and Chile (2007-2018). Using a difference-in-difference approach, we evaluated changes in the prevalence of past-year, past-month, any risky and frequent cannabis use following enactment (2014) and implementation (2016) of cannabis legalization among the full sample of secondary students and among students who reported past-year/month use. We examined changes separately for students aged 12-17, and students for whom cannabis became legally accessible, ages 18-21. SETTING Uruguay and Chile (2007-2018). PARTICIPANTS Secondary school students in 8th , 10th , and 12th grade (n=204,730). MEASUREMENTS Past-year and past-month cannabis use; any risky cannabis use measured with the Cannabis Abuse Screening Test (CAST); and frequent cannabis use (10+ days in the past-month). FINDINGS We found a decrease in past-year and past-month use following enactment or implementation. Among students ages 18-21, post-enactment, we observed a transitory increase in 2014 that decreased thereafter for: any risky use among those who reported past-year use (prevalence difference [PD]=13.5%; 95% confidence interval [CI]: 2.0, 24.9), frequent use in the full sample (PD=4.5%; 95%CI: 1.0, 8.1), and frequent use among those who reported past-month use (PD=16.8%; 95%CI: 1.9, 31.8). CONCLUSION The legalization of recreational cannabis in Uruguay was not associated with overall increases in either past-year/past-month cannabis use or with multi-year changes in any risky and frequent cannabis use among young people.

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