Under the influence: examination of prevalence and correlates of alcohol and marijuana consumption in relation to youth driving and passenger behaviours in Canada. A cross-sectional study.

BACKGROUND: Consequences of alcohol- and drug-impaired driving affect youth disproportionately. We describe individual- and area-level characteristics associated with risky driving and passenger behaviours among grade 9-12 students in Canada.

METHODS: The 2014-2015 Canadian Student Tobacco, Alcohol and Drug Survey was administered to 24 650 students in provincially generalizable samples. Dichotomous outcomes included ever and last-30-day driving after drinking alcohol, ever and last-30-day driving after using marijuana, and ever and last-30-day reporting of being a passenger with a driver who had been drinking or using marijuana.

RESULTS: A total of 9.1% (99% confidence interval 7.9-10.3) of grade 11-12 students reported ever driving after drinking, and 9.4% (99% confidence interval 8.3-10.4) reported ever driving after using marijuana. Almost half (48%) of grade 11-12 students reported ever participating in any risky driving or passenger behaviour. Over one-third (35%) of grade 9-12 students reported ever riding with a driver who had been drinking, and 20% reported ever riding with a driver who had been using marijuana. Logistic regression models showed that boys had higher odds of risky driving behaviours relative to girls, whereas girls had higher odds of risky passenger behaviours relative to boys. Students from rural schools had higher odds of drinking and driving and of riding with a driver who had drunk relative to students from urban schools. There were significant differences in risky driving and passenger behaviours by province.

INTERPRETATION: A substantial number of Canadian youth reported risky driving and passenger behaviours, which varied by individual and area-level characteristics. Federal marijuana policy should aim to reduce the prevalence of drug-impaired driving. Additional provincial policies to prevent impaired driving are needed.