Exploring the Relationship Between Depressive Symptoms, Allostatic Load, and Income Inequality in US Adults Aged 20 and Older

Allostatic load, reflecting the cumulative physiological impact of persistent stress on the body, has been recognized as a correlate of physical health outcomes. Despite well-documented associations between allostatic load and physical health, there is limited understanding of its connections to depressive symptoms. In particular, less is known about how socioeconomic status (SES) may moderate this relationship, despite theoretical rationale for such an interaction. This study utilizes large diverse nationally representative data from the National Health and Nutrition Examination Survey (NHANES) to investigate the association between allostatic load, depression, and poverty-to-income-ratio (PIR). We conducted a cross-sectional secondary analysis of NHANES data (2005-2018) for adults (defined as 20-year or older), exploring the link between allostatic load (AL), measured through various physiological markers, and depressive symptoms assessed with the Patient Health Questionnaire (PHQ). The analysis included weighted binomial regressions to report Incidence Rate Ratio (IRR) that controlled socioeconomic status and health-related behaviors. After controlling socioeconomic status and health-related behaviors, our findings demonstrate a significant association between high allostatic load and increased depressive symptoms (IRR: 1.22, CI = 1.13-1.32). This suggests that the physiological toll of chronic stress, as captured by allostatic load, is independently linked to elevated levels of depressive symptoms in a nationally representative sample. This study contributes to the understanding of the association between physiological stress, allostatic load and PIR on a national scale. It underscores the importance of recognizing allostatic load as a potential target for interventions aimed at preventing or mitigating depressive symptoms in the population.