Background: Numerous studies have established a link between adverse childhood experiences (ACEs) and the development of depression in later life. However, the interactive relationships between ACEs, depression, and chronic diseases are still not well understood. In this study, the aim was to investigate the impact of ACEs on depressive trajectories among middle-aged and elderly individuals in China, as well as to examine the mediating roles of chronic diseases in this association. Methods: Data were drawn from 6921 participants aged 45 and older, using the China Health and Retirement Longitudinal Study (CHARLS) data from 2011, 2013, 2015, and 2018, combined with the 2014 life history survey. Depressive symptom scores were assessed using the widely recognized CES-D-10 scale. The trajectories of depressive symptoms were identified via group-based trajectory modeling (GBTM). The association between ACEs and depressive trajectories was analyzed using multinomial logistic regression, and the KHB method was employed to test the mediating effects of different chronic diseases. Results: The age of the 6921 participants was 57.2 ± 8.0 years, with females comprising 53.9% and males 46.1%. We found that approximately 70% of Chinese middle-aged and older adults had experienced at least one ACE, and 4.8% had experienced four or more ACEs. The following four distinct trajectories of depressive symptoms were identified: continuing-low (N = 1897, 27.4%), continuing-low-to-middle (N = 2937, 42.4%), continuing-middle-to-high (N = 1649, 23.8%), and continuing-high (N = 438, 6.3%). Compared to individuals without ACEs, those with four or more ACEs had a significantly higher likelihood of following the continuing-low-to-middle trajectory (OR = 2.407, 95%CI: 1.633–3.550), the continuing-middle-to-high trajectory (OR = 7.458, 95%CI: 4.999–11.127), and the continuing-high trajectory (OR = 20.219, 95%CI: 12.115–33.744), rather than the continuing-low trajectory. Exposure to a greater number of ACEs was associated with an increased risk of following an adverse trajectory of depressive symptoms. Multiple chronic diseases significantly mediated the relationship between ACEs and depressive trajectories, with arthritis or rheumatism exerting the largest mediating effect, followed by digestive and respiratory diseases. Conclusions: These findings indicated that ACEs were associated with a higher risk of worse depressive symptom trajectories, with different chronic diseases mediating this relationship. Therefore, developing public measures to prevent ACEs can reduce the risk of chronic diseases and depression in middle-aged and elderly people. Additionally, strengthening the prevention and management of chronic diseases in individuals exposed to ACEs may further reduce their subsequent risk of depression.
