Trends in cannabis use over time among Canadian youth: 2004-2014.

Cannabis is the most commonly used illicit substance among Canadian youth. The current study examined national trends in cannabis use among Canadian youth from 2004/05 to 2014/15 using nationally representative data from the Canadian Student Tobacco, Alcohol and Drugs Survey (CSTADS). Data were collected from students in Grades 7 to 12 as part of the Canadian Student Tobacco, Alcohol and Drugs Survey (formerly the Youth Smoking Survey) using a repeat-cross sectional survey across 6 biennial survey waves between 2004 and 2014 (N = 243,057). Regression models examined factors associated with cannabis use in the past 12 months, perceived ease of access, and a multilinear regression examined age of initiation across survey cycles. The findings indicate that use of cannabis in the past 12-months significantly decreased among Canadian youth. Past-year use peaked in 2008/09 at 27.3%; compared to 16.5%, in 2014/15. Mean age of initiation did not vary over time, while youth in recent cycles reported that cannabis was more difficult to access: in 2006/07, 77.1% reported that it would be easy to access cannabis compared to 49.0% in 2014/15. Overall, cannabis use among Canadian youth appears to have peaked around 2008/09, with substantial declines over the past decade. It will be critically important to examine any changes in patterns of use following legalization of non-medical cannabis in Canada.