Analysis of trends in the prevalence of cannabis use in Canada, 1985 to 2015.

BACKGROUND: The Canadian federal government has committed to legalize, regulate, and restrict non-medical cannabis use by adults in 2018. To prepare for monitoring the health, social and economic impacts of this policy change, a greater understanding of the long-term trends in the prevalence of cannabis use in Canada is needed.

DATA AND METHODS: Nine national surveys of the household population collected information about cannabis use during the period from 1985 through 2015. These surveys are examined for comparability. The data are used to estimate past-year (current) cannabis use (total, and by sex and age). Based on the most comparable data, trends in use from 2004 through 2015 are estimated.

RESULTS: From 1985 through 2015, past-year cannabis use increased overall. Analysis of comparable data from the Canadian Tobacco Use Monitoring Survey and the Canadian Tobacco, Alcohol and Drugs Survey for the 2004-to-2015 period suggests that use was stable among 15- to 17-year-old males, decreased among 15- to 17-year-old females and among 18- to 24-year-olds (both sexes), and increased among people aged 25 or older.

DISCUSSION: According to data from national population surveys, since 2004, cannabis use was stable or decreased among youth, and rose among adults. Results highlight the importance of consistent monitoring of use in the pre-and post-legalization periods.