Grant: Project Grant

Legalization of recreational cannabis use in Canada will have important implications for road safety. In 2012, collisions in Canada caused by cannabis resulted in estimated costs of over $1 billion. Evidence suggests that legalization in some jurisdictions has led to increases in driving under the influence of cannabis (DUIC). While collisions and fatalities caused by DUIC have been most common among young drivers, the increase in DUIC following legalization appeared to be a result of increases in DUIC among older drivers compared to youth. Several impaired driving countermeasures (e.g., graduated licensing) are designed specifically to target young drivers. If legalization results in larger numbers of older cannabis-using drivers, it is important that we understand how cannabis affects driving in both young and older drivers in order to target countermeasures appropriately. It is well known that alcohol increases collision risk among young drivers at a faster rate than among older drivers, which has been attributed to inexperience with both alcohol and the driving task. Evidence regarding possible differences in cannabis use frequency in young versus older populations has varied; but, across populations, use frequency impacts the drug's cardiovascular and cognitive effects and the subjective drug high produced. This study will assess age differences in the effects of smoked cannabis on simulated driving and will explore factors that may significantly affect these differences. Young (19-25 years) and middle-aged (35-45 years) occasional and frequent cannabis users will smoke a cannabis or placebo cigarette in each of two sessions. Before and after smoking, participants will operate a driving simulator, complete cognitive/psychomotor tests, and provide oral fluid and blood samples. Results of the study will have immediate implications for impaired driving prevention, legislation and policy, including standards by which enforcement officers judge driver impairment.