Self-reported collision risk associated with cannabis use and driving after cannabis use among Ontario adults.

Objective: This study examined the effects of cannabis use and driving after cannabis use on self-reported collision involvement within the previous 12 months while controlling for demographics, driving exposure, binge drinking, and driving after drinking based on a large representative sample of adults in Ontario.

Methods: Data are based on the CAMH Monitor, an ongoing cross-sectional telephone survey of Ontario adults aged 18 and older, conducted by the Centre for Addiction and Mental Health. Data on drivers who reported driving at least one kilometer per week and who responded to the collision item from 2002 to 2007 were merged into one data set (n = 8481). Logistic regression analysis of self-reported collision risk posed by cannabis use (lifetime and past 12 months), driving after cannabis use (past 12 months), and driving after drinking among drinkers (past 12 months) was implemented, controlling for the effects of gender, age, region, income, education, marital status, kilometers driven in a typical week, and consuming five or more drinks of alcohol on one occasion (past 12 months). Due to list-wise deletion of cases the logistic regression sample was reduced (n = 6907).

Results: Several demographic factors were found to be significantly associated with self-reported collision involvement. The logistic regression model revealed that age, region, income, marital status, and number of kilometers driven in a typical week, were all significantly related to collision involvement, after adjusting for other factors. Respondents who reported having driven after cannabis use within the past 12 months had increased risk of collision involvement (odds ratio [OR] = 1.84) compared to those who never drove after using cannabis, a greater risk than that associated with having reported driving after drinking within the past 12 months (OR = 1.34).

Conclusion: Further investigation of the impact of driving after cannabis use on collision risk and factors that may modify that relationship is warranted.