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The association between recreational cannabis legalization, commercialization and cannabis attributable emergency department visits in Ontario, Canada: an interrupted time-series analysis


Background and Aims — Recreational cannabis was legalized in Canada in October 2018. Initially, the Government of Ontario (Canada’s largest province) placed strict limits on the number of cannabis retail stores before later removing these limits. This study measured changes in cannabis attributable emergency department (ED) visits over time, corresponding to different regulatory periods.

Design — Interrupted time series design using population-level data. Two policy periods were considered; recreational cannabis legalization with strict store restrictions (“RCL”, 17 months), and legalization with no store restrictions (“recreational cannabis commercialization, RCC”, 15 months) which coincided with the COVD-19 pandemic. Segmented Poisson regression models were used to examine immediate and gradual effects in each policy period.

Setting — Ontario, Canada

Participants — All individuals aged 15-105 years (n=13.8 million) between January 2016 and May 2021.

Measurements — Monthly counts of cannabis attributable ED visits per capita and per all-cause ED visits in individuals aged 15+ (adults) and 15-24 (young adults) years.

Findings — We observed a significant trend of increasing cannabis attributable ED visits prelegalization. RCL was associated with a significant immediate increase of 12% (Incident Rate Ratio [IRR] 1.12 95% confidence interval [CI] 1.02 – 1.23) in rates of cannabis attributable ED visits followed by significant attenuation of the pre-legalization slope (monthly slope change IRR 0.98 95% CI 0.97 – 0.99). RCC and COVID-19 were associated with immediate significant increases of 22% (IRR 1.22 95%CI 1.09 – 1.37) and 17% (IRR 1.17 95%CI 1.00 – 1.37) in rates of cannabis attributable visits and the proportion of all-cause ED visits attributable to cannabis, respectively, with insignificant increases in monthly slopes. Similar patterns were observed in young adults.

Conclusions — In Ontario, Canada, cannabis attributable emergency department visits stopped increasing over time following recreational cannabis legalization with strict retail controls but then increased during a period coinciding with cannabis commercialization and the COVID-19 pandemic.



Myran D, Pugliese M, Tanuseputro P, Cantor N, Rhodes E, Taljaard M. Addiction. 2022; 117(7):1952-60. Epub 2022 Feb 16.

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