Prelegalisation patterns and trends of cannabis use among Canadian youth: results from the COMPASS prospective cohort study

Abstract

Objective: Canada federally legalised recreational cannabis use among adults in October 2018. The impact this will have on Canadian youth is cause for concern. The current study examined changes in youth cannabis use over the time prior to legalisation to explore the impact of the beginning federal discourse around legalisation during the 2016/2017 school year.

Design: COMPASS, a prospective cohort study based on annual self-administered questionnaires.

Setting: Ontario and Alberta during the first 6 years of the COMPASS study (2012/2013 to 2017/2018).

Participants: Canadian grade 9-12 students attending secondary schools participating in COMPASS. In total, 2 30 404 questionnaires were included in the analysis (Y1: 2012/2013, n=24 173; Y2: 2013/2014, n=45 298; Y3: 2014/2015, n=42 355, Y4: 2015/2016, n=40 436; Y5: 2016/2017, n=37 060; Y6: 2017/2018, n=34 897).

Primary and secondary outcome measures: Lifetime cannabis use, past-year cannabis use, weekly cannabis use, ease of access to cannabis and age at first cannabis use.

Results: Cannabis never-use decreased between Y5 and Y6. Changes in age at first cannabis use mirrored this trend, with male students consistently starting younger. Cannabis access rates increased from Y4, mainly led by female students. Lifetime and past-year use rates were lowest in Y4 then increased in Y5 and Y6 due to a rise in the occasional use more common among female students, who reported use increases first. Non-white students were more likely use cannabis, with black and Aboriginal students the only two groups consistently reporting more weekly than occasional use, though with opposing trajectories. Overall, Aboriginal students had the highest odds of reporting lifetime, past-year and weekly use among the demographic groups examined.

Conclusion: After a steady decrease in patterns of cannabis among youth over several years, it appears that there has been a gradual increase in cannabis use among youth following the start of discourse around cannabis legalisation, with some populations of youth being at greater risk.

Keywords: epidemiology; public health; substance misuse.

Figure 1

Rates of lifetime and past-year cannabis use among youth participating in the COMPASS study (Ontario and Alberta, Canada). Total proportion of COMPASS students reporting lifetime and past-year cannabis use (A) in total and (B) by gender each school year from Y1 (2012/2013) to Y6 (2017/2018). (C, D) Total proportion of COMPASS students grouped by race/ethnicity reporting (C) lifetime and (D) past-year cannabis use. Y1, 2012/2013; Y2, 2013/2014; Y3, 2014/2015; Y4, 2015/2016; Y5, 2016/2017; Y6, 2017/2018.

Figure 2

Average age at first cannabis use and rates of easy access to cannabis among youth participating in the COMPASS study (Ontario and Alberta, Canada). Grade 12 COMPASS students reporting (A, B) average age at first cannabis use (A) overall and by gender and (B) by ethnicity each school year from Y1 (2012/2013) to Y6 (2017/2018). (C, D) Total proportion of grade 9–12 COMPASS students who think cannabis is easy to access (C) overall and by gender and (D) by ethnicity. Y1, 2012/2013; Y2, 2013/2014; Y3, 2014/2015; Y4, 2015/2016; Y5, 2016/2017; Y6, 2017/2018.

Figure 3

Rates of weekly and occasional cannabis use among youth participating in the COMPASS study (Ontario and Alberta, Canada). Total proportion of COMPASS students reporting weekly (one to six times a week or daily) and occasional (two to three times a month or less) cannabis use (A) in total and (B) by gender each school year from Y1 (2012/2013) to Y6 (2017/2018). (C, D) Total proportion of COMPASS students grouped by race/ethnicity reporting (C) weekly and (D) occasional cannabis use. Y1, 2012/2013; Y2, 2013/2014; Y3, 2014/2015; Y4, 2015/2016; Y5, 2016/2017; Y6, 2017/2018.