INTRODUCTION: There has been increasing attention on preventing problematic youth substance use in light of concerns about rates of use and policy changes in Canada. Strengths-based approaches that emphasize protective factors, including positive mental health, are at the forefront of current prevention recommendations. However, there is a dearth of research on the association between positive mental health and substance use among youth. This study examines the associations between cannabis and alcohol use among youth and positive mental health as measured through the lens of self-determination theory.

METHODS: Secondary analyses of the 2014/2015 Canadian Student Tobacco, Alcohol and Drugs Survey (CSTADS) were conducted. Participating Grade 7 to 12 students residing in Canada completed the Children's Intrinsic Needs Satisfaction Scale (CINSS), which measures autonomy, competence and relatedness, and answered questions that measure past 30-day and more frequent cannabis use, alcohol use and binge-drinking. The associations between autonomy, competence and relatedness and substance use, stratified by sex, were examined using logistic regression.

RESULTS: Fully adjusted models revealed that relatedness and competence were associated with lower odds of 30-day and more frequent cannabis use, alcohol use and binge-drinking. Higher autonomy was associated with higher odds of these behaviours. All associations were significant with the exception of competence and more frequent cannabis use among boys, and autonomy and more frequent alcohol use among girls.

CONCLUSION: The findings offer new evidence on the associations between positive mental health and substance use among youth, specifically how autonomy, competence and relatedness are associated with cannabis use, alcohol use and binge-drinking. This evidence can be used to inform health promotion and substance use prevention programs.