Depressive symptoms, a common disorder that severely impairs psychosocial functioning and lowers the quality of life, was reported to affect 39 % of the elderly (65+) and 45 % of the most elderly (80+) in China (Fang et al., 2020; Malhi and Mann, 2018). Therefore, primary preventions, such as adopting healthy lifestyles, are of great importance (Kandola et al., 2020; Sarris et al., 2020).

Life-course disadvantages, including childhood and adulthood disadvantages, refer to a wide spectrum of stressful socioeconomic, interpersonal, mental, and health-related conditions across the life-course (Chiao et al., 2014; Madero-Cabib et al., 2019; Siegrist, 2016). Previous research has widely established that individuals with life-course disadvantages are more likely to experience depressive symptoms and develop unhealthy lifestyles (Chen et al., 2021; Dokkedal-Silva et al., 2021; Loxton et al., 2021; Yu and Liu, 2021). However, given the stigma of mental illness and cultural differences (Zhang and Li, 2011), related evidence in the Chinese population is much less adequate than that in western populations.

Limited evidence, to the best of our knowledge, has comprehensively demonstrated the association of life-course disadvantages and various lifestyles with depression in China. According to earlier research, sleep quality mediated the association between life-course disadvantages and depression in western countries (Fusco et al., 2021; Rojo-Wissar et al., 2019). Boisgontier et al. (2020) also indicated that physical activity reduced the effect of adverse childhood experiences on depression. However, these studies were constrained due to the insufficient definition of life-course disadvantages and the limited variety of healthy lifestyles. Additionally, given the stark differences between Chinese and Western lifestyle habits and the heavy burden of depressive symptoms in the elderly Chinese (Meng et al., 2020), it is worth exploring whether adopting healthy lifestyles can assist Chinese seniors who are at high risk for depression, but few studies have been conducted to date.

To fill in these knowledge gaps, we utilized the China Health and Retirement Longitudinal Study (CHARLS) and hypothesized that unhealthy lifestyles mediated the associations between life-course disadvantages and depressive symptoms and that adopting healthy lifestyles can dilute the depressive risks attributed to life-course disadvantages in middle-aged and older Chinese.