Social capital and physical health: An updated review of the literature for 2007-2018

Purpose: Social capital is frequently indicated as a determinant of population health. Despite an increase in the frequency of public health studies including such measures, our understanding of social capital's effects on health remains unclear. In 2008, a systematic review of the first decade of research on social capital and health was published in the textbook Social Capital and Health. Our study intends to update and expand upon this original review to account for developments in the literature over the second decade of research on social capital and health. Methods: We employed a systematic review of empirical studies investigating the relationship between measures of social capital and physical health outcomes published between January 1, 2007 and December 31, 2018. To identify potential studies, we conducted searches of PubMed, Embase, and PsychINFO databases in January 2019 using combinations of social capital and physical health search terms. Results: We identified 1,608 unique articles and reviewed 145 studies meeting our inclusion criteria. The most frequently examined health condition was self-reported health (57%), followed by mortality (12%), cardiovascular diseases (10%), obesity (7%), diabetes (6%), infectious diseases (5%), and cancers (3%). Of these studies, 127 (88%) reported at least partial support for a protective association between social capital and health. However, only 41 (28%) reported exclusively positive findings. The majority (59%) of results were mixed, suggesting a nuanced relationship between social capital and health. This finding could also be indicative of differences in study design, which showed substantial variation. Conclusions: Despite limitations in the literature, our review chronicles an evolution in the field of social capital and health in terms of size and sophistication. Overall, these studies suggest that social capital may be an important protective factor for some physical health outcomes, but further research is needed to confirm and clarify these findings.