Abstract
BACKGROUND: Many youth report driving under the influence of cannabis (DUIC) and riding with a cannabis-impaired driver (RWCD), and many perceive that cannabis causes limited impairment. We examined associations of perceived risk of regular cannabis use with DUIC and RWCD, exploring differences by sex and rural setting. METHODS: In a cross-sectional study, we examined DUIC and RWCD among high school students in grades 11 and 12 who participated in the 2016-2017 Canadian Student Tobacco, Alcohol and Drugs Survey. Private and public schools across 9 Canadian provinces were included. New Brunswick and the 3 territories were not included. Multinomial logistic regression models generated adjusted and unadjusted models for the associations. RESULTS: A total of 52 103 students in grades 7-12, from 117 school boards and 699 schools, participated in the survey. The survey response rate was 76.2% (n = 52 103/68 415). In total, 14 520 students in grades 11 and 12 participated in the survey. Greater perceived risk of regular cannabis use was associated with reduced risk of DUIC and RWCD in a dose-response manner. Students perceiving that regular cannabis use posed great risk had an adjusted relative risk (RR) of 0.06 (95% confidence interval [CI] 0.04-0.10) of DUIC in the past 30 days compared with students perceiving that regular use posed no risk. Students perceiving that regular cannabis use posed great risk had an adjusted RR of 0.09 (95% CI 0.07-0.12) of RWCD in the past 30 days compared with students perceiving no such risk. Associations were consistent for male and female students and for those living in urban and rural areas. INTERPRETATION: Students perceiving minimal risk from cannabis use reported greater engagement in cannabis-related risky driving behaviours. Given the importance of youth perceptions in shaping driving and passenger behaviours, efforts must be made to disseminate appropriate information regarding cannabis-related driving risks to high school students.