Risk Perceptions Associated with Driving Under the Influence of Cannabis: Examining Differences between Medical and Non-Medical Cannabis Users

Author(s): Wickens, McDonald, Stoduto, Di Ciano, Hamilton, Elton-Marshall, Nigatu, Mann

Slidedeck Presentation:

Med vs Rec Cannabis and DUIC Risk Perception - Presentation - Wickens



Risk perception and attitudes are a strong determinant of behaviour. In the context of road safety, reduced perception of potential harm resulting from cannabis use is associated with greater risk of driving under the influence of cannabis (DUIC). Growing evidence suggests that DUIC increases risk of motor vehicle collisions (MVCs). According to the 2020 Canadian Cannabis Survey, 27 percent of Canadians aged 16+ years used cannabis for non-medical (i.e., recreational) purposes in the previous 12 months, and 14 percent used cannabis for medical purposes. Only a few studies have examined differences in cannabis-related risk perceptions among medical and non-medical users, and these have generated mixed findings. Among a sample of adolescents in Canada, medical cannabis users were more likely to perceive cannabis as harmful. However, among a sample of drivers aged 16+ years in the USA, no differences between medical and non-medical users were found in the percentage of participants who believed DUIC is safe.


To compare DUIC-related risk perceptions among individuals who use cannabis exclusively for non-medical purposes versus those who use cannabis for exclusively medical or for both medical and non-medical purposes.


Data were drawn from a regionally stratified cross-sectional general population telephone survey of adults (18+ years) in Ontario, Canada conducted from 2014 to 2019. Respondents reporting past-year operation of a vehicle and past-year use of cannabis were selected (N=1392). Log Poisson regression models with robust standard error estimation were conducted for three attitudes: disagree that DUIC increases MVC risk, agree that DUIC is safer than driving under the influence of alcohol (DUIA), agree that chances of being caught by police for DUIA higher than DUIC. In addition to type of cannabis user (medical versus non-medical-only), covariates included demographic characteristics, past-year drinker or non-drinker of alcohol, and past-year cannabis use frequency (monthly versus less than monthly).


Adjusting for other covariates, regression analyses indicated that medical cannabis users were more likely than non-medical users to agree that DUIC is safer than DUIA (Adjusted Prevalence Ratio=1.30, 95%CI=1.00, 1.69, p=0.045). No other differences between medical and non-medical cannabis users were found.


Policy and prevention initiatives to reduce risky or unhealthy behaviours can only be effective when targeting the correct audience with an appropriate message. Although no difference between medical and non-medical cannabis users was found in perceptions of collision risk associated with DUIC or risk of police enforcement, the perception that DUIC is safer than DUIA was stronger among medical than non-medical users. Recognizing that the shift in public perception of DUIA as a high-risk behaviour contributed to reductions in incidence of DUIA, results of the current study support education campaigns emphasizing similarities in the dangers of DUIA and DUIC that specifically target medical users.


Further research examining the strength of association between risk perceptions and DUIC for each type of cannabis user and other potential differences between medical and non-medical cannabis users could benefit road safety initiatives.