Sex-Specific Association Between Zero-Calorie Beverage Consumption and Depressive Symptoms in Korean Adolescents: A Nationwide Cross-Sectional Study

Background/Objectives: Zero-calorie beverages (ZCB) are increasingly consumed by adolescents, yet their relationship with mental health remains unclear, and whether any association differs by sex has not been established. We examined the association between ZCB consumption and depressive symptoms in a nationally representative sample of Korean adolescents, with sex as a prespecified effect modifier. Methods: This cross-sectional study analyzed 50,972 adolescents aged 12–18 years (50.9% male; mean age, 15.0 years) from the 2025 Korea Youth Risk Behavior Web-based Survey. Self-reported ZCB consumption during the previous 7 days and depressive symptoms during the previous 12 months were assessed. ZCB consumption was categorized as none, ≤2/week, 3–6/week, or ≥1/day. Survey-weighted logistic regression estimated adjusted odds ratios (aORs) with 95% confidence intervals (CIs), with non-consumers as the reference. Effect modification by sex was assessed using interaction terms. Results: Depressive symptoms were reported by 12,954 adolescents (25.4%). ZCB consumption was associated with higher odds of depressive symptoms across consumption categories (aOR for ≥1/day 1.76, 95% CI 1.45–2.13; p for trend < 0.001), after adjustment for sociodemographic and lifestyle covariates. The association appeared stronger among females than among males (aOR 1.14 [95% CI 1.11–1.18] vs. 1.05 [1.02–1.08]; p for interaction < 0.001), though significant in both sexes, and persisted after additional adjustment for co-consumed sugar-sweetened and high-caffeine beverages. Conclusions: In this nationally representative sample, daily ZCB consumption was associated with depressive symptoms, with a stronger association observed among females. Prospective studies are warranted to clarify temporality and underlying mechanisms.