Grant: Project Grant

Canada was the second country to legalize cannabis at the Federal level, and, with increased access, it is imperative to understand best practices around cannabis use. Co-administration of cannabis and tobacco in a single cigarette is a common practice, with users reporting that tobacco makes the cannabis less harsh. Despite the prevalence of co-use of these substances, laboratory studies into the impact of tobacco on cannabis-related harms, such as impaired driving, is lacking. An understanding of the interactions between tobacco and cannabis on the experience of cannabis may help to provide evidence-based guidance on the safest use of cannabis. The purpose of the present study will be to evaluate the effects of tobacco, cannabis or combinations of tobacco and cannabis on driving, cognition, subjective effects and blood THC (the psychoactive component of cannabis). Driving will be assessed using a state-of-the-art driving simulator that allows for the safe and objective measurement of the effects of intoxicating substances on driving. Participants will be regular users of cannabis and will be invited to the lab for four test sessions. In these test sessions they will drive the simulator and undergo cognitive tests before and after smoking: 1) cannabis; 2) tobacco; 3) cannabis + tobacco; or 4) placebo. Outcomes will be measured at several time points after smoking the product. Participants will also give blood for determination of levels of THC, and will complete subjective effects questionnaires both before and after smoking the cigarette. This study will be one of the first experimental laboratory studies of the reasons behind co-administration of tobacco and cannabis. This study will provide important insights into the best use of cannabis, and we will work closely with advisors on developing campaigns to inform the public about the relative benefits and risks of mixing cannabis with tobacco.