Bidirectional association of psychopathology and cannabis use: Results from the Swiss study on recreational cannabis access via pharmacies.

Although associations between cannabis use and mental health have been widely examined, temporal relationships between cannabis use patterns and psychopathological symptoms in regulated settings remain underexplored. We investigated longitudinal associations between cannabis use patterns (frequency, quantity, and problematic use) and psychopathological symptoms (depression, anxiety, and psychosis) over one year of pharmacy-based regulated cannabis access in Switzerland among 378 adult regular cannabis users. Assessments were conducted at baseline, 6 months, and 12 months using validated instruments (PHQ-9, GAD-7, adapted ERIraos) and standardized measures of cannabis use (use days in the past 30 days, quantity per use day, CUDIT-R). Cross-lagged linear mixed-effects models and Bonferroni correction for multiple testing were applied. Problematic cannabis use (CUDIT-R) prospectively predicted higher depressive symptom load (β = 0.113, p < 0.001) and higher anxiety symptom load (β = 0.066, p = 0.015). Anxiety symptoms were associated with subsequent increased cannabis use frequency (β = 1.055, p = 0.047). No longitudinal associations were observed for psychosis symptoms. These findings suggest that problematic cannabis use, rather than frequency or quantity alone, may be particularly relevant for depressive and anxiety symptom trajectories in regulated cannabis access settings and should be considered in clinical assessment and public health discussions surrounding cannabis regulation.