Fig. 1.

Cannabis use among three longitudinal cohorts of high school students who were attending grades 9–12 in Alberta (AB) and Ontario (ON) and taking part in COMPASS (Canada) starting at grade 9 in the 2013-14 (Cohort 1; C1), 2014-15 (Cohort 2; C2), and 2015/16 (Cohort 3; C3) school years. Students reported cannabis ever use (any previous use), current use (once a month or more often). Among students indicating ever use, frequency of use is differentiated by occasional use (up to three times a month) and regular use (once a week or more often).