Fatal Car Collisions After Marijuana Legalized Interview with:

Sarah Windle

Sarah Windle

Sarah Windle, MPH
PhD Student in Epidemiology
Department of Epidemiology, Biostatistics, and Occupational Health
McGill University (Montréal, Québec, Canada) What is the background for this study?

Response: Concerns have been raised about the potential for increases in impaired driving following the legalization of recreational cannabis use in Canada in October 2018. Data from Statistics Canada suggest that cannabis use in the previous three months increased among adults (15 and older) from 14% before legalization in 2018 to 17% in 2019. Among those users with a driver’s license, 13% reported driving within two hours of cannabis use. While this proportion remained the same before and after legalization, this indicates that the absolute number of individuals who reported driving within two hours of use has increased following legalization (due to an increase in the number of users). What are the main findings?

Response: We analysed data from 11 jurisdictions in the United States which legalized recreational cannabis prior to 2019; legalization was associated with a 15% increase in fatal motor vehicle collisions. Previous studies have also suggested the potential for small increases in fatal motor vehicle collisions following recreational cannabis legalization in United States jurisdictions. Regulatory and public health measures (e.g., THC limit laws, educational campaigns) may prevent potential increases in cannabis-impaired driving in Canada. Healthcare professionals also have the opportunity to educate patients concerning cannabis-impaired driving. For example, Canada’s Lower Risk Cannabis Use guidelines provide evidence-based steps such as choosing lower potency products, limiting to occasional use, and waiting at least six hours prior to driving after consuming cannabis. What should readers take away from your report?

Response: Evidence suggests that there is the potential for a small but important increase in fatal motor vehicle collisions following recreational cannabis legalization. However, federal impaired driving regulations and educational campaigns may prevent increases in cannabis-impaired driving in Canada. Healthcare professionals should provide patients with clear, evidence-based guidance for safer cannabis use. What recommendations do you have for future research as a result of this work?

Response: Further robust analyses concerning the association between recreational cannabis legalization and impaired driving should be conducted as more data become available. Knowledge gaps also remain concerning the practical application of field sobriety tests and biochemical measures to detect cannabis-impaired driving, as well as how healthcare professionals should determine fitness to drive, particularly for long-term regular users of cannabis.

Any disclosures? The authors have no disclosures.


Impaired driving and legalization of recreational cannabis

Sarah B. WindleCrystal SequeiraKristian B. FilionBrett D. ThombsPauline ReynierRoland GradCarolyn Ells and Mark J. Eisenberg


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Last Updated on April 6, 2021 by Marie Benz MD FAAD