Association between hemoglobin-to-red cell distribution width ratio and depression in Chinese adults: a population-based cross-sectional study

HRR may indicate an independent, linear inverse association with elevated depressive symptoms (SDS ≥ 53) in Chinese adults, with strong effects in older populations. As a cost-effective hematological biomarker, HRR could support scalable elevated depressive symptoms (SDS ≥ 53) stratification and prevention strategies to complement other risk factors for elevated depressive symptoms, particularly in aging groups, and these findings warrant validation in prospective studies.