Associations between metabolic syndrome and depression, and the mediating role of inflammation: Based on the NHANES database

Abstract

Background

Individuals with metabolic syndrome (MetS) have an increased risk of depressive symptoms, with inflammation hypothesized to mediate this association. This study used data from the National Health and Nutrition Examination Survey (NHANES) (2015–2020) to investigate the relationship between MetS and depression and assess the mediating role of inflammatory markers.

Methods

This cross-sectional study included 20,520 participants. MetS was defined using the NCEP ATP III criteria. Depressive symptoms were assessed with the Patient Health Questionnaire-9 (PHQ-9), with scores ≥10 indicating clinical significance. Inflammatory markers evaluated included C-reactive protein (CRP), white blood cell count (WBC), and neutrophil-to-lymphocyte ratio (NLR), among others. Multivariable linear and logistic regression models were applied to examine associations, and mediation analysis was conducted to evaluate the potential mediating effects.

Results

Overall, 7.64 % of participants exhibited depressive symptoms. MetS was associated with an increased risk of depression in both females (OR: 1.49, 95 % CI: 1.28–1.74) and males (OR: 1.32, 95 % CI: 1.09–1.60) after adjusting for confounders. Among MetS components, central obesity, hypertension, and dyslipidemia demonstrated the strongest associations with depression. Inflammatory markers mediated 26.79 % of the MetS-depression relationship, with CRP contributing the largest proportion (17.24 %).

Conclusion

MetS and its components significantly increase the risk of depressive symptoms, with the relationship partially mediated by inflammatory markers. Chronic inflammation may play a critical role in linking MetS to depression, underscoring the importance of integrated management strategies targeting both metabolic and mental health.