Substance use behaviours have been found to cluster in youth, and cannabis use has been previously linked to tobacco and e-cigarette use. The objective of the current study was to examine the bidirectional associations between cannabis, e-cigarette, and cigarette use among a large sample of Canadian secondary school students. A sample of students in grades 9–11 (n = 14,652) from Ontario and Alberta, Canada who participated in two waves of the COMPASS Study (Time 1...