Grant: Project Grant

Cannabis and alcohol are widely used among young adults in Canada and both substances are often used at the same time. Rates of simultaneous use of alcohol and cannabis may increase as a result of legalization and increased access to cannabis in Canada. Combining cannabis with alcohol can increase risk for harms such as psychological and physical symptoms, social problems, and risk for substance use disorders. However, little is currently known about real-time patterns of simultaneous use of cannabis and alcohol, or how these contribute to risk for harms above and beyond using either substance alone. This study will use real-time mobile data collection to examine patterns of simultaneous cannabis and alcohol use in individuals' daily lives. Young adults who regularly use cannabis and alcohol will be asked to track their use of both substances using a smartphone app for three, 21-day periods spaced 6 months apart. On mornings following alcohol and/or cannabis use, participants will complete measures of substance use consequences. Data will be used to examine patterns of simultaneous use, including the frequency of co-use, the overall quantity of each substance used, and the temporal ordering of each substance (e.g., cannabis before alcohol or vice versa). Contextual influences on simultaneous use and the subjective effects of combining cannabis with alcohol will also be investigated. Further, the unique risks of combining cannabis and alcohol (e.g., risky behaviours, hangovers) will be examined relative to the use of either substance alone. Finally, changes in patterns of simultaneous use will be examined over a one-year period in relation to health outcomes such as symptoms of substance use disorders. The findings will improve our understanding of the unique health risks of cannabis and alcohol co-use, which will have direct implications for public health policies as cannabis becomes legal in Canada.