Grant: Operating Grant

Motor vehicle collisions are the leading cause of death for young people. We have recently found that driving after using cannabis is more common among young Canadian drivers than driving after drinking. While this observation raises concerns, the effects of cannabis on driving-related skills in this age group are not well understood. As well, evidence suggests that residual effects of cannabis on driving-related skills may be observed up to 24 hours later. These residual effects may have important implications for the effects of cannabis use on collisions risk, but little evidence on them is available. This study will examine the effects of a single dose of cannabis on driving-related skills immediately following consumption, 24 hours later, and 48 hours later. To date the residual effect at 48 hours has not been examined. A total of 128 subjects aged 19 and 20 will be randomly assigned to smoke either a placebo or cannabis (12.5% THC potency) cigarette. Participants must be regular users of cannabis, but not heavy/problem users, and must be free of any mental/physical health concerns that would contraindicate an acute dose of cannabis. Following a practice session, participants will attend 3 testing days: drug-administration, 24-hour follow-up, and 48-hour follow-up. The effects of cannabis/placebo on performance of driving-related skills using a high-fidelity driving simulator will be assessed on each testing day. The effects of cannabis on mood, cognition, memory and complex reaction time will also be assessed. Identifying factors that affect the collision risks experienced by young drivers is a public health priority. While many young people believe that cannabis does not impair driving, some recent studies suggest that these may be very dangerous beliefs. This study will provide important information on how cannabis may affect the driving skills of young drivers, to inform efforts to understand and address cannabis-related collisions in this age group.