Moderate alcohol consumption and depression - a longitudinal population-based study in Sweden.

BACKGROUND AND AIMS: The interrelationship between alcohol consumption and depression is complex, and the direction of the association is unclear. We investigated whether alcohol consumption influences the risk of depression while accounting for this potential bidirectionality.

METHODS: A total of 10 441 individuals participated in the PART study in 1998-2000, 8622 in 2001-2003, and 5228 in 2010. Participants answered questions on their alcohol consumption, symptoms of depression, childhood adversity, and sociodemographic, socioeconomic, psychosocial, and lifestyle factors. A total of 5087 participants provided repeated information on alcohol consumption. We used marginal structural models to analyze the association between alcohol consumption and depression while controlling for previous alcohol consumption and depressive symptoms and other time-varying confounders.

RESULTS: Non-drinkers had a higher depression risk than light drinkers (≤7 drinks/week) (risk ratio: 1.7; 95% confidence interval 1.3-2.1). Consumers of seven-fourteen drinks/week had a depression risk similar to that of light drinkers. Hazardous drinking was associated with a higher risk of depression than non-hazardous alcohol consumption (risk ratio: 1.8, 95% confidence interval: 1.4-2.4).

CONCLUSION: Light and moderate alcohol consumption and non-hazardous drinking were associated with the lowest risk of subsequent depression after accounting for potential bidirectional effects. Hazardous drinking increased the risk of depression.