Association Between Systemic Inflammation Response Index and Specific Depressive Symptoms: Evidence From a Cross‐Sectional Survey

OBJECTIVE: Depression is a highly heterogeneous disorder with broad symptomatology. Systemic inflammation has been implicated in the underlying pathophysiology of depression. This study was to investigate the association between the systemic inflammation response index (SIRI) and specific depressive symptoms. METHODS: Data from the National Health and Nutrition Examination Survey were employed in this cross-sectional study. SIRI was derived from peripheral neutrophil, monocyte, and lymphocyte counts. The Patient Health Questionnaire-9 (PHQ-9) was administered to assess depressive symptoms. Multivariable logistic regression and generalized additive models were employed to examine the association between SIRI and specific depressive symptoms, adjusting for sociodemographic, behavioral, and medical factors. RESULTS: Analysis of data from 30,763 participants demonstrated significant associations between SIRI and specific depressive symptoms, including anhedonia (odds ratio [OR] = 1.12, 95% confidence interval [CI]: 1.03-1.21), sleep disturbance (OR = 1.11, 95% CI: 1.04-1.19), fatigue (OR = 1.11, 95% CI: 1.04-1.19), and appetite change (OR = 1.10, 95% CI: 1.01-1.19). Nonlinear relationships were observed for anhedonia and sleep disturbance, with inflection points at SIRI = 0.67. Subgroup analyses revealed that SIRI was associated with anhedonia in adults aged 18-39 years and males, multiple depressive symptoms in Mexican American/Hispanic individuals, sleep disturbance and fatigue in adults aged 40-59 years, and fatigue in non-Hispanic Whites. CONCLUSIONS: There is a certain degree of cross-sectional association between SIRI and specific depressive symptoms. Future research should focus on longitudinal studies and symptom homogeneity to elucidate the underlying inflammatory mechanisms in depression.