Objective  To investigate the effects of individual social capital on depressive symptoms among older couples across different socioeconomic statuses (SES) using the actor-partner interdependence model (APIM).

Methods A cross-sectional survey was conducted using a staged sampling method, involving 245 older couples from communities in Chengdu, China. Data on household SES, individual social capital, and depression levels were collected. Pearson correlation analysis was performed to examine the relationships among these variables, and the APIM was applied to analyze the actor and partner effects of individual social capital on depression across different SES groups.

Results  The prevalence of depressive symptoms was 38.2%. Individual social capital of the husbands and wives was negatively correlated with their personal depression levels (actor effects among the husbands: r = －0.218, P < 0.01; those among the wives: r = －0.323, P < 0.01) and with the spouse's depression levels (partner effects: husband on wife, r = －0.185, P < 0.01; wife on husband: r = －0.183, P < 0.01). Among high-SES couples, the husband's social capital had a protective effect only on his own depression (β = －0.242, 95% CI: －0.462 to －0.054). In contrast, among low-SES couples, the wife's individual social capital exhibited a protective effect against depressive symptoms both for herself (β = －0.658, 95% CI: －0.848 to －0.456) and for the husband (β = －0.379, 95% CI: －0.630 to －0.143).

Conclusion  Individual social capital among older couples demonstrates both actor and partner effects on depression levels, with distinct pathways of influence observed across different levels of SES. These findings highlight the importance of considering socioeconomic status when designing interventions to enhance social capital and improve mental health outcomes in older couples.