BackgroundDepression is a significant global health concern, projected to become the leading disease burden. Vascular burden has been implicated in the pathogenesis of depression. Conversely, whether depression independently influences the process of vascular aging is unknown. This study aims to investigate the mutual relationship between vascular age and depression. MethodsUtilizing data from the National Health and Nutrition Examination Survey (NHANES), the study included 27,764 participants after exclusions. Depression was assessed using the Patient Health Questionnaire (PHQ-9). Vascular aging was assessed by estimated pulse wave velocity (ePWV) and the heart age/vascular age (HVA) based on Framingham Risk Score (FRS). The study employed weighted logistic regression and Cox proportional hazards models to analyze the association between vascular age and depression as well as its mortality risk. Mendelian randomization was utilized to explore the causal associations. ResultsIndividuals with depression exhibited a higher risk of an advanced vascular age over their chronological age. Mendelian randomization analysis indicated a causal relationship between depression and arterial stiffness. A significant association was found between vascular age and depression incidence with odds ratios ranging from 1.10 to 1.38. As vascular age increased, the risk of mortality in individuals with depression increased by 22 % and 46 %, respectively. LimitationsThe study design limits the exploration of the dynamic relationship between changes in vascular age and depression due to the single timepoint measurement. ConclusionThis study highlights the bidirectional relationship between depression and vascular age. Vascular age is a significant biomarker for the risk and prognosis of depression, while depression may contribute to vascular aging, which underscores the importance of integrated strategies for managing both vascular health and depression.