Trends in Canadian Cannabis Consumption Over Time: A Two-step Meta-analysis of Canadian Household Survey Data

Aims: To estimate temporal trends in cannabis consumption in the Canadian household population using national survey data and map changes in cannabis consumption postlegalization in 2018. Methods: In a 2-step meta-analysis approach, we first analyzed each survey year separately by estimating the weighted past-year prevalence (%) of self-reported cannabis use (including just once) with its 95% confidence intervals (CIs). In the next step, to produce aggregate data for each survey year, we pooled prevalences using the DerSimonian and Laird random-effects (determined a priori) meta-analysis model packages in R to estimate the between-study variance (tau(2)) for the inverse variance method, and the Freeman-Tukey Double arcsine transformation. Results: In total, 29 Statistics Canada survey iterations met eligibility for inclusion in the meta-analysis. Reported pastyear prevalences for cannabis use ranged from 4.2% in 1993 to 27% in 2021. The overall prevalence of past-year cannabis use was 11.4% (95% CI, 9.7%-13.3%; 22 surveys; 53,712/474,888 participants; I-2= 99.8%; tau(2)= 0.0048). There was a significant increase in cannabis past-year prevalence in subgroup meta-analyses (P< 0.0001) comparing postlegalization [2018-2021: 25.0% (95% CI, 23%-27%), I-2= 96%] to prelegalization [1985-2017: 9.9% (95% CI, 9%-11%), I-2= 99%]. There was also a significant time trend, with a steady increase in the reported past-year cannabis prevalence over time from 1985 through 2021. Notably, the most recent national estimate of cannabis prevalence from 2021 was nearly 6 times the first estimate from 1985 (27% vs. 5%). Conclusions: The present study is the first to synthesize Canadian household survey data to estimate the temporal trends in cannabis consumption and is the first meta-analysis examining both the prevalence and changes postlegalization of cannabis use in Canada. The evidence indicates increasing past-year cannabis consumption and time, with a statistically significant increase postlegalization. The public health implications of these changes require further study.