Consistent low-to-moderate alcohol consumption in early-to-middle adulthood predicted lower depressive symptoms at age 50; his work offers preliminary evidence that such protective effects may be causal

Visontay, Rachel, Louise Mewton, Tim Slade, Izzuddin M. Aris, and Matthew Sunderland. 2021. “Moderate Alcohol Consumption and Depressive Symptoms: A Marginal Structural Model Approach Promoting Causal Inference.” OSF Preprints. November 19. doi:10.31219/osf.io/e2gcm

Abstract

Importance: Prevention of depressive symptoms and disorders is a key public health priority but requires an improved understanding of modifiable risk and protective factors. A salient unanswered question in this context is whether the apparent protective effect of alcohol against depression may be causal.

Objective: To compare the effects of consistent abstinence, occasional, moderate, and heavy alcohol consumption throughout early-to-middle adulthood on depressive symptoms at age 50.

Design: This secondary analysis of the National Longitudinal Survey of Youth (NLSY79) cohort employed a marginal structural model approach in assessing the relationship between alcohol consumption in early-to-middle adulthood (29-37 through 41-49) and depressive symptoms at age 50. Alcohol consumption was based on measurements at 1994, 2002, and 2006, covariates at 1992, 1994, and age 40 (1998-2006), and outcome at age 50 (2008-2016).

Setting: The NLSY79 is a nationally representative, population-based cohort study.

Participants: 5,667 eligible participants at baseline provided valid data on alcohol consumption, depressive symptoms, and covariates of interest.

Exposure: Alcohol consumption was categorised as either abstinence, occasional, moderate, or heavy drinking in 1994, 2002, and 2006.

Main Outcome and Measure: Depressive symptoms at age 50 as measured by the Centre for Epidemiological Studies-Depression Scale short form (CES-D-SF).

Results: Of the 5,667 eligible participants at baseline, 2,862 [50.50%] were female and the mean age was 30.81 [2.24], with 3,593 participants providing valid outcome data for analysis. Results of linear contrasts from marginal structural models were consistent with a J-shaped relationship, where both consistent occasional (b=-0.84, CI= -1.47, -.11) and consistent moderate (b=-1.08, CI=-1.88, -.20) drinkers had significantly reduced predicted CES-D-SF scores at age 50 compared to consistent abstainers. Consistent heavy drinkers were predicted to have increased depressive symptoms, but this was not statistically significant (b=0.34, CI=-0.62, 1.25). In sex-stratified analyses, results were similar for females and males.

Conclusions and Relevance: In this secondary analysis of longitudinal data accounting for time-varying exposure and confounding, consistent low-to-moderate alcohol consumption in early-to-middle adulthood predicted lower depressive symptoms at age 50, compared with those abstaining from alcohol. This work offers preliminary evidence that such protective effects may be causal.