The effect size and nonlinearity of the relationship between cannabis consumption and consumer self‐perceived mental health: A study based on eight national surveys in Canada

Previous research suggests a negative association between cannabis consumption and consumer mental health, but the magnitude and linearity of this association require further investigation. Therefore, this study analyzed eight suitable national survey datasets from Statistics Canada from 2009 to 2021. In the general population, the mean effect size between cannabis use (yes/no) and self‐perceived mental health is negative but very small in magnitude ( = −0.096). Moreover, in the cannabis user sub‐population, the mean effect size between cannabis usage frequency and mental health is small in magnitude ( = −0.157). More importantly, among cannabis users, a nonlinear negative relationship between cannabis use frequency and mental health was identified. Specifically, as cannabis use becomes more frequent and people's self‐perceived mental health worsens, the association becomes stronger. These findings have significant implications for social marketing and health promotion.