Examining the links between COVID-19 seropositivity, metabolic syndrome and depressive symptoms: evidence from ENSANUT 2021–2022

Background The COVID-19 pandemic has affected mental health, with a particular impact on depressive symptoms. Metabolic syndrome is also linked to depression, but their combined effects remain unclear. Aims To examine the independent and combined effects of COVID-19 seropositivity and metabolic syndrome on depressive symptoms, considering demographic and health-related factors. Method A cross-sectional analysis was conducted using 2021–2022 Encuesta Nacional de Salud y Nutrición data. Depressive symptoms were assessed with the Center for Epidemiological Studies Depression Scale (CESD-7), including subscales for positive affect, negative affect and somatic symptoms. COVID-19 seropositivity was determined through seroprevalence data, and metabolic syndrome was defined using Adult Treatment Panel III criteria. Logistic and linear regression models evaluated associations between COVID-19 seropositivity, metabolic syndrome and depressive symptoms, adjusting for demographic and health factors. Results Among 10 890 adults, 3312 (30.4%) had depressive symptoms. COVID-19 seropositivity ( n = 7790, 71.7%) was associated with higher odds of depressive symptoms (odds ratio 1.22, 95% CI 1.08–1.38) and increased CESD-7 scores (coefficient 0.39, 95% CI 0.19–0.58), particularly negative affect (coefficient 0.16, 95% CI 0.05–0.27) and somatic symptoms (coefficient 0.23, 95% CI 0.12–0.34). Metabolic syndrome was associated with depressive symptoms (odds ratio 1.17, 95% CI 1.02–1.33), mainly through negative affect (coefficient 0.27, 95% CI 0.12–0.41). No significant interaction was found between COVID-19 seropositivity and metabolic syndrome. Conclusions COVID-19 seropositivity and metabolic syndrome independently increase depression risk, highlighting the need for integrated mental and metabolic health screening.