Cannabis Consequences Predicted Later Depression More Than Depression Predicted Cannabis Use

Using seven assessments over two years, significant bidirectional within-person relationships were found between cannabis consequences and internalizing symptoms, but the primary direction was from cannabis consequences to increased depressive symptoms, not from depression to increased cannabis use. Importantly, cannabis use frequency alone did not predict later symptoms; only negative consequences did. The bidirectional relationships were more pronounced among females and those with clinically elevated internalizing symptoms at baseline.

Longitudinal study of 961 high-risk emerging adults (54% female) from two cohorts (Ontario, Canada and Tennessee, USA), assessed at 4-month intervals over 2 years (2018-2020). Latent curve models with structured residuals examined within-person and between-person bidirectional relationships.

This clarifies a longstanding debate: it is the problems from cannabis use (not the use itself) that predict worsening mental health. This distinction has practical implications, as interventions that reduce cannabis-related harm could prevent downstream depression even without full abstinence.

The finding that consequences, not frequency, drive the mental health link suggests that harm reduction approaches, which aim to reduce negative outcomes without requiring abstinence, may be effective for preventing depression in young cannabis users.

High-risk sample may not generalize to general population. Self-report measures. Study period overlapped with early COVID-19 pandemic. Four-month intervals may miss shorter-term dynamics. Consequences and symptoms may share reporting bias.