To explore the dynamic developmental trajectory of depressive symptoms among middle-aged and older adults in China, and to analyze the influences of childhood trauma and cognitive function on the trajectory.

Based on data from the China Health and Retirement Longitudinal Study from 2011 to 2020, a prospective cohort study was conducted on 7916 middle-aged and older adults across 5 waves of surveys (T1=2011, T2=2013, T3=2015, T4=2018, T5=2020). Childhood trauma questionnaire, cognitive function questionnaire, and Center for Epidemiologic Studies Depression Scale were used to measure the experience of childhood trauma, cognitive function level, and depression level respectively. Pearson correlation analysis was employed to explore the correlations among variables. A latent growth curve model was constructed, and the fit of the model was evaluated based on indicators such as comparative fit index (CFI), Tucker-Lewis index (TLI), standardized root mean square residual (SRMR), and root mean square error of approximation (RMSEA). The nonlinear characteristics of the developmental trajectory of depression were depicted through intercept (I), slope (S), and quadratic slope (Q) parameters. The regression coefficient (β) and its 95% confidence interval (CI) were estimated using the Bootstrap method to explore the influencing factors of the developmental trajectory of depression in middle-aged and older adults.

① Childhood trauma was significantly positively correlated with cognitive function at each time point (r=0.044 to 0.077, P<0.001), and with depression at each time point (r=0.057 to 0.095, P<0.001). Cognitive function was significantly negatively correlated with depression at each time point (r=-0.257 to-0.133, P<0.001). ② Quadratic growth model demonstrated good fit (CFI=0.997, TFI=0.995, SRMR=0.017, RMSEA=0.029). Depressive symptoms exhibited a quadratic growth trend of "decreasing first, then increasing" over time (I=8.067, S=-0.158, Q=0.033, P<0.001). ③ After incorporating the variable of childhood trauma, childhood trauma significantly positively predicted the initial level of depression (β=0.294, 95%CI: 0.208 to 0.381, P<0.001), but had no significant predictive effect on the linear slope or quadratic slope. ④ After further incorporating the cognitive function variable, the cognitive function at each of the 5 time points could significantly negatively predict the depression at the same time period (TI: β=-0.194, 95%CI: -0.233 to-0.155; T2: β=-0.135, 95%CI: -0.161 to-0.109; T3: β=-0.131, 95%CI: -0.161 to-0.100; T4: β =-0.134, 95%CI: -0.163 to-0.106; T5: β =-0.177, 95%CI: -0.220 to-0.134; all P<0.001).

The development trajectory of depression among middle-aged and older adults displays a nonlinear trend of quadratic growth. Childhood trauma is a risk factor for the initial level of depression in them, while cognitive function serves as a protective factor for the developmental trajectory of depression.