This study examined the extent to which SC moderated the association between caregiving to older parents or a spouse and caregiver’s PD. Unlike most preceding studies, this study applied a DMD model analysis, which allowed us to control for an individual’s time-invariant attributes in a dynamic framework. This approach, combined with the limitation of the sample to those who provided no care in the previous year, mitigated the biases that cannot be controlled for when using cross-sectional regression. In addition, we compared the results across different age groups, considering the possibility of a change in the relevance of SC for caregivers’ mental health as caregivers aged. The key findings and their implications are summarized as follows:
First, the results confirmed the moderating effect of SC on the association between caregiving and PD for both women and men, a result consistent with previous studies that showed the favorable impact of SC on health [16–19]. Even after controlling for individual-specific fixed effects and other factors, the DPD model results suggest that SC mitigated a substantial portion of the adverse impact of caregiving on caregivers’ mental health. This implies that socially isolated caregivers may face higher risks of deterioration in their psychological well-being, pointing to the need for policy measures to help middle-aged and older adults create and enhance their SC.
Second, the moderating effect of SC increased as caregivers aged. The adverse impact of caregiving tended to be more serious for older caregivers, especially for women. This result highlighted health problems related to the issue of “elderly-for-elderly care.” It should be noted, however, that the moderating effect of SC tended to offset the enhanced adverse impact of caregiving on PD. As a result, the probability of PD for female caregivers with SC declined, albeit slightly, as age advanced. Similarly, the probability for male caregivers with SC to experience PD remained relatively low and not significantly different from that of non-caregivers. Many studies have provided evidence for the importance of SC for older adults’ well-being [16, 18], presumably because the opportunities to participate in social activities are likely to become more limited as people age. The results of this study underscored the importance of SC for older caregivers, by showing that SC prevented an age-related increase in the adverse impact of caregiving on a caregiver’s mental health.
Third, we observed a substantial difference in the moderating effect of SC. We found that the effect differed substantially between women and men. As already observed in previous studies, there are consistently higher levels of PD in women [31–33]. Notably, the proportion of the association moderated by SC (–β3/β1) was somewhat more limited for women than for men. Considering the magnitude of the interaction effect between caregiving and SC (|β3|) was almost in the same range or even larger for women (especially for older age groups), as seen in Table 3, an SC’s lower moderating effect for women can be accounted for by a closer association between caregiving and PD, that is, higher value of β1, for women. This appears to have partly reflected that women undertake more intensive caregiving; indeed, the average hours for caregiving per week was 19.0 hours (SD: 23.7 hours) among female caregivers, as compared to 13.2 hours (SD: 23.7 hours) among male caregivers. Hence, the lower moderating effect of SC for women did not mean a limited importance of SC for women. In fact, that effect increased substantially as female caregivers got older, as clearly seen in Fig. 2. Meanwhile, our results showed a more limited increase in the moderating effect of SC for men as they got older. This may reflect that a man spends longer in the workplace, which was likely to reduce the chances of enhancing SC, as compared to women.
We recognize that this study has several limitations and that many issues remain to be addressed. Importantly, we did not fully address the potential endogeneity of SC. DPD model analysis controlled for the confounding effects of an individual’s attributes on the associations between key variables, and we found that the estimation results differed substantially from pooled cross-sectional models, as already suggested by previous fixed-effects model studies [34, 35]. However, we could not exclude the possibility that caregiving affects SC during the caregiving process , especially as we focused on the individual-level SC. Second, we did not examine the evolution of caregivers’ PD over time. Instead, we focused on the relatively short-term association between the onset of caregiving and a caregiver’s PD in order to mitigate potential simultaneity biases. Going forward, we should extend the analysis to the evolution of a caregiver’s PD over time [37–39]. Examining that must involve a two-way interaction with SC, as mentioned above. In addition to these methodological limitations, caution should be exercised when generalizing the results. The relevance of caregiving and caregivers’ mental health may depend heavily on formal long-term care provisions, family care norms, and other socio-cultural backgrounds .