Does Obesity Increase the Risk of Depression in Youth? A Stratified Meta-Analysis of Longitudinal and Cross-Sectional Evidence.

Obesity and depression in childhood and adolescence represent major public health concerns, yet the nature and direction of their association remain incompletely understood. In the present study, we conducted a systematic review and stratified meta-analysis of epidemiological studies examining the relationship between obesity and depression in youth populations. A total of 945 records were identified through database searches, of which 18 studies met the inclusion criteria for the review. To ensure greater conceptual consistency, quantitative synthesis was restricted to studies examining categorical obesity (typically defined as body mass index (BMI) ≥ 95th percentile) and binary depression outcomes, which formed the longitudinal and cross-sectional meta-analytic cores, analyzed separately. Our longitudinal meta-analysis (k = 4; N = 5581) indicated that obesity was associated with an increased likelihood of subsequent depression (OR = 2.05, 95% CI: 1.40-2.99), whereas the cross-sectional meta-analysis (k = 6; N = 20,278) showed a weaker and non-significant association (OR = 1.40, 95% CI: 0.98-2.00) with moderate heterogeneity. Additional studies that could not be pooled due to differences in exposure or outcome definitions were integrated through narrative synthesis and showed mixed and generally less consistent patterns, broadly supporting the distinction between longitudinal and cross-sectional evidence. Overall, our findings suggest that obesity during childhood and adolescence is associated with an increased likelihood of subsequent depression, while concurrent associations appear more heterogeneous and more difficult to interpret. By distinguishing between study designs and prioritizing comparable effect estimates, this study provides a more transparent synthesis of the current evidence on the relationship between obesity and depression in youth.