Associations of Changes in Alcohol Consumption on the Risk of Depression/Suicide Among Initial Nondrinkers.

Although prior studies showed the association between the amount of alcohol ingestion and the risk of depression and suicide, there has been a lack of research considering changes in alcohol intake over time. This research aimed to assess the associations of alcohol consumption level changes and the risk of depression and suicide among initial nondrinkers. Using data from the National Health Insurance Service in South Korea between 2002 and 2019, a total of 129,446 subjects were included and monitored from January 1, 2011, to December 31, 2019, of which 102,721 were never drinkers and 26,725 were former drinkers. For depression, the follow-up periods ranged from 0.01 to 9.00 years (mean 8.65, median 9.00 years). Moreover, for suicide, the follow-up periods ranged from 0.03 to 9.00 years (mean 8.99, median 9.00 years). To ensure robust results, the model was adjusted for several confounders in three steps: Model 1 was adjusted for sociodemographic factors (age and sex), Model 2 included additional lifestyle factors (household income, smoking status, and physical activity) in addition to Model 1 variables, and Model 3 included all variables from Model 2 and incorporated further variables including body mass index (BMI), systolic blood pressure, fasting serum glucose, total cholesterol, and the Charlson Comorbidity Index (CCI). The Cox proportional hazard regression was utilized to estimate the adjusted hazard ratio (aHR) and 95% confidence intervals (CIs) for depression and suicide risk after an increase in alcohol consumption. Individuals who increased alcohol consumption lightly up to one glass per day had a reduced risk of depression (aHR, 0.91; 95% CI, 0.84-0.98) compared with individuals who maintained their nondrinking status at the third medical checkup. Notably, stratified analyses indicated that the associations were only evident in those younger than 60 years and those physically active. Additionally, among former drinkers, those who increased their alcohol intake to four or more glasses per day had an increased risk of depression (aHR, 1.31; 95% CI, 1.04-1.66). However, individuals who initiated drinking between two and four glasses of alcoholic beverages per day were found to have a higher risk of suicide (aHR, 2.25; 95% CI, 1.31-3.87) relative to those who continued to abstain from drinking. Our findings suggest that small increases in alcohol intake among the initial nondrinkers are associated with a reduced risk of depression, whereas moderate-to-heavy increments in alcohol consumption are associated with a detrimental risk of suicide. This study has several limitations including the low number of suicide events, reliance on self-reported alcohol consumption which may introduce underreporting bias, and the exclusion of important confounding variables such as educational attainment and dietary factors. Furthermore, the study population was exclusively Korean, limiting the generalizability of the findings to other ethnic groups.