Grant: CIHR Fellowship

Canada will legalize the sale and possession of cannabis in October 2018, marking a foundational shift in national substance use policy as cannabis joins alcohol as a legal psychoactive drug. Research studying recent events in the United States has shown that cannabis legalization has led to increased cannabis use and cannabis use disorders; however, the simultaneous effect on alcohol use and alcohol use disorders is not clear. It is important to study these two now-legal substances in parallel as alcohol is used more widely and is responsible for greater health harms than cannabis in Canada. This program of research, completed as a collaboration between the Canadian Institute for Substance Use Research and the National Drug Research Institute (Australia), will evaluate the effect of cannabis legalization on alcohol and cannabis use and associated mental health disorders. Will cannabis legalization lead to an increase in the prevalence of use of cannabis and alcohol among Canadians? Will Canadians experience higher rates of alcohol use disorders and cannabis use disorders after legalization? Or may Canadians substitute cannabis use for alcohol use and therefore experience fewer negative health consequences overall? Changes in prevalence and patterns of cannabis and alcohol use resulting from legalization will be studied using Canadian survey sources. Health records will be analyzed to estimate the rate of cannabis use and alcohol use disorders, for a period before and after legalization. Time series methods will then be employed to study the unique effect of legalization, using Australian states as control groups where legalization did not take place. This proposed research will provide answers to important questions regarding recent substance use policy change in Canada. The results will be both relevant and timely, providing critical information to policymakers in Canada, Australia and around the world regarding the health impacts of cannabis legalization.