Internet Usage, Social Participation, and Depression Symptoms Among Middle-Aged and Older Adult Chinese Individuals Before and During the COVID-19 Pandemic: Evidence From the China Health and Retirement Longitudinal Observational Study.

Background: While the relationship between internet usage and depression, and the mediating role of social participation in this association, has garnered significant attention, the COVID-19 pandemic has disrupted traditional forms of social participation. The extent to which this disruption has altered the association remains underexplored. Objective: This study aims to examine the impact of internet usage on depressive symptoms among middle-aged and older adults and to assess how the mediating role of social participation differs before and during the COVID-19 pandemic. Methods: Data for this study were sourced from the fourth wave (2018: 15,326 observations) and the fifth wave (2020: 15,758 observations) of the China Health and Retirement Longitudinal Study. A 2-way fixed-effects model incorporating an instrumental variable was employed to investigate the relationship between internet usage and depressive symptoms among middle-aged and older adults. Furthermore, a mediation effect model was applied following propensity score matching to assess changes in the mediating role of social participation on the relationship between internet usage and depressive symptoms before and during the pandemic, as well as to explore changes in 3 internet usage functions. Subgroup analyses based on age and urban-rural residence were performed to assess heterogeneity in this association. Results: The average Center for Epidemiological Studies Depression Scale (CESD-10) score among middle-aged and older Chinese people increased from 1.94 in 2018 to 1.98 in 2020. Internet usage was negatively associated with depressive symptoms (β=-.041; P<.01), with social participation serving as a partial mediator. The proportion of the mediating effect of social participation on the relationship between distinct internet usage functions and depression shifted during the pandemic: the social function declined from 12.55% in 2018 to 9.30% in 2020, while the informational and recreational function increased from 7.53% and 11.29% in 2018 to 8.85% and 16.37% in 2020, respectively. Both the total and indirect effects were statistically significant across subgroups, with a higher mediation proportion observed among rural residents and women than among urban residents and men. Conclusions: Internet usage was negatively associated with depressive symptoms among middle-aged and older adults. Despite a noticeable increase in depression scores in 2020 compared with 2018, the mediating effect of social participation diminished, while the direct effect of internet usage became more pronounced during the pandemic. These findings underscore the need to prioritize mental health recovery in this population, promote diverse forms of social participation, and leverage the internet's potential to enhance social participation and mental well-being.