Cannabis use and psychological distress: An 8-year prospective population-based study among Swedish men and women

Previous studies have reported positive associations between cannabis use and mental health problems. However, it has not been possible to draw a definitive conclusion regarding the causal direction between cannabis use and impaired mental health. This study aimed at examining possible associations between cannabis use and psychological distress (as measured by the General Health Questionnaire, GHQ-12) in men and women respectively, using both measures as both exposure and outcome.

Data were obtained from a cohort study (the Stockholm Public Health Cohort) with an 8-year follow-up in the general population in Stockholm County, Sweden. The study sample comprised 19,327 men and women, aged 18-84years, who answered surveys in 2002 and 2010.

Cannabis use was associated with increased odds ratios (OR) for psychological distress in women at 8-year follow-up, with OR=1.37 [1.1-1.7, 95% CI], but not in men; OR=1.14 [0.9-1.5, 95% CI]. In women, this association remained when adjusted for potential confounders (tobacco smoking, alcohol consumption, socioeconomic position (SEP) and unemployment); OR=1.27 [1.0-1.6, 95% CI]. Moreover, women reporting psychological distress at baseline had an increased risk of cannabis use at follow-up; OR=1.40 [1.1-1.8 95% CI]. However, this association was no longer statistically significant when adjustments were made for baseline cannabis use, OR=1.10 [0.8-1.5, 95% CI].

This study revealed that, in women, cannabis use was associated with an increased risk of psychological distress eight years later. Optimal interventions to identify these women seem warranted.