Cannabis legalization and driving under the influence of cannabis and driving under the influence of alcohol among adult and adolescent drivers in Ontario, Canada (2001-2019)

Background: The impacts of cannabis legalization on driving under the influence of cannabis and driving under the influence of alcohol among adults and adolescents were examined in Ontario, Canada. Methods: Data were sourced from adult (N=38,479) and adolescent (N=23,216) populations -based surveys (2001-2019). The associations between cannabis legalization and driving within an hour of using cannabis and driving within an hour of drinking two or more drinks of alcohol were quantified using logistic regression, with testing of multiplicative interactions between cannabis legalization and age and sex. All analyses were conducted separately for adults and adolescents and restricted to participants with a valid driver's license. Results: Cannabis legalization was not associated with driving within an hour of using cannabis among adults (OR, 95% CI: 1.21, 0.69-2.11). However, a multiplicative interaction indicated that there was an increased likelihood of driving within an hour of using cannabis among adults >= 55 years of age (4.23, 1.85-9.71) pre -post cannabis legalization. Cannabis legalization was not associated with driving within an hour of using cannabis among adolescents (0.92, 0.72-1.16), or with driving within an hour of consuming two or more drinks of alcohol among adults (0.78, 0.51-1.20) or adolescents (0.87, 0.42-1.82). Conclusions: An increased likelihood of driving under the influence of cannabis among adults >= 55 years of age was detected in the year following cannabis legalization, suggesting the need for greater public awareness and education and police monitoring and enforcement concerning driving under the influence of cannabis, particularly among older adults.