Age of first use, current marijuana use and driving after use among Canadian high school students

Early exposure to marijuana may have lasting effects into adulthood given that adolescence is a critical period during which most substance use is initiated. Recreational marijuana recently became legal in Canada, with a legal age of purchase set as either 18 or 19 years, depending on the province. Historically, the mean age of onset for marijuana use among youth occurs at a much younger age. The current study examined the association between age at first use of marijuana with current marijuana use patterns and driving after use among high school students. Data on 24,630 high school students (grades 9-12) were from the 2014-2015 Canadian Student Tobacco, Alcohol and Drugs Survey. We restricted our analyses to the students who reported having ever used marijuana and had data on age at first marijuana use (n = 6709). Multivariable logistic and negative binomial regressions were performed to examine the association between current marijuana use patterns and age at first marijuana use. Students with younger age at first use of marijuana had significantly higher odds of current marijuana use, a higher frequency of consumption, and were more likely to drive after use of marijuana. Effective enforcement of age restriction laws in combination with other prevention efforts may be beneficial in delaying the age of onset of marijuana until late adolescence and early adulthood.