BACKGROUND: Adverse experiences are critical determinants of late-life depressive symptomatology. Understanding how these experiences influence later-life health outcomes remains a research priority. This study examines the longitudinal associations between self-reported adverse childhood experiences (ACEs) and adverse adult experiences (AAEs) with depressive symptoms in older adults, as well as the underlying mechanisms. METHODS: A sample of 3941 adults aged ≥45 years from the China Health and Retirement Longitudinal Study (CHARLS) was analyzed. K-means for Longitudinal Data (KML), Logistic regression, and Bayesian Kernel Machine Regression (BKMR) models were employed to assess the effects of adverse experiences. Subgroup and mediation analyses were also performed. RESULTS: The high depressive symptomatology cluster (n = 1432) demonstrated significant associations with six ACEs: childhood hunger (OR = 1.23, 95%CI:1.03-1.47), dangerous growth environments (OR = 1.34, 95%CI:1.09-1.65), childhood loneliness (OR = 1.45, 95%CI:1.20-1.74), bullying (OR = 1.2, 95%CI:1.01-1.43), parental depression (OR = 1.80, 95%CI:1.50-2.16), and parental disability (OR = 1.44, 95%CI:1.03-2.02). Comprehensive effect estimation of ACEs indicated an 85.9% probability of a high depression score for those with all adverse experiences. AAEs like prolonged bed rest (OR = 1.39, 95%CI:1.08-1.79), and lifetime discrimination (OR = 1.37, 95%CI:1.12-1.66) independently predicted symptom severity. Effect modification analysis revealed stronger ACE impacts among individuals with higher cognitive reserve (OR = 3.32, 95%CI:2.34-4.70). Mediation analysis identified arthritis or rheumatism as a partial mediator of the ACE-depression pathway (natural indirect effect = 1.04, 95%CI:1.02-1.05). CONCLUSIONS: Self-reported ACEs and AAEs demonstrate persistent associations with depressive symptoms in later life, mediated by chronic morbidity and moderated by cognitive reserve.