Does cannabis use predict the first incidence of mood and anxiety disorders in the adult population?

AIMS

To investigate whether cannabis use predicted the first incidence of mood and anxiety disorders in adults during a 3-year follow-up period.

DESIGN AND PARTICIPANTS

Data were derived from the Netherlands Mental Health Survey and Incidence Study (NEMESIS), a prospective study in the adult population of 18-64 years. The analysis was carried out on 3881 people who had no life-time mood disorders and on 3854 people who had no life-time anxiety disorders at baseline.

MEASUREMENTS

Life-time cannabis use and DSM-III-R mood and anxiety disorders, assessed with the Composite International Diagnostic Interview (CIDI).

FINDINGS

After adjustment for strong confounders, any use of cannabis at baseline predicted a modest increase in the risk of a first major depression (odds ratio 1.62; 95% confidence interval 1.06-2.48) and a stronger increase in the risk of a first bipolar disorder (odds ratio 4.98; 95% confidence interval 1.80-13.81). The risk of 'any mood disorder' was elevated for weekly and almost daily users but not for less frequent use patterns. However, dose-response relationships were less clear for major depression and bipolar disorder separately. None of the associations between cannabis use and anxiety disorders remained significant after adjustment for confounders.

CONCLUSIONS

The associations between cannabis use and the first incidence of depression and bipolar disorder, which remained significant after adjustment for strong confounders, warrant research into the underlying mechanisms.