Analysis of trends in the prevalence of cannabis use and related metrics in Canada.

BACKGROUND: The Canadian federal government legalized non-medical cannabis use by adults in October 2018. Ongoing monitoring of the effects of the change is needed because uncertainty remains about the impact of the legislation on cannabis use behaviours and whether the impact will affect some more than others. DATA AND METHODS: Data from the Canadian Tobacco, Alcohol and Drugs Survey and the Canadian Tobacco Use Monitoring Survey were used to examine longer-term (historical) rates of use during 2004 to 2017. Five iterations of the National Cannabis Surveys (NCS) (2018-2019) were used to examine current use (overall, daily or almost daily (DAD), quantities, and types of products) in the months before and after legalization.
RESULTS: From 2004 through 2017 cannabis use decreased among 15 to 17 year olds, remained stable for 18 to 24 year olds, and increased among adults aged 25 to 64. During 2018 and into 2019, rates of cannabis use increased overall from 14% to 18%; with statistically significant increases also for males generally (16% to 22%) and males aged 18 to 64. Rates of cannabis use remained largely stable for females (13%) and seniors (4%). In 2019, about 60% of consumers reported using one cannabis product; use of dried cannabis (flower/leaf) was the most common (84.2%). The average user consumed 27.5 grams of dried cannabis (flower/leaf) over three months; amounts consumed varied depending on use frequency (e.g. occasional users: 2.6 grams/3 months versus DAD users: 62.6 grams/3 months). DISCUSSION: Results highlight the importance of understanding pre-legalization behaviours as changes in use after legalization may have begun prior to the legislation. NCS allows for the early impacts of legalisation to be examined and provides a picture of not only changes in who is using but also what and how much.