The concept of “social capital” was developed by sociologists to describe the resources available to individuals through their membership in community networks. Analogous to financial capital, which resides in people's bank accounts, or human capital, which is embodied in individuals' investment in education and job training, social capital exists as the structure and quality of social relationships between individuals. An individual’s level of social capital might include membership in community organizations, mutual trust and help within the neighborhood and organizations, or ability to receive information.  Such assets of people have seemed to promote physical health, and indeed U.S. states with low levels of social capital have been shown to have higher mortality rates and worse health status than those with high levels.

The mechanisms linking social capital to health have not been fully clarified. At the level of communities and individuals social capital is believed to promote health by buffering stress and providing social support, as well as offering some control over unhealthy health behaviors such as underage smoking and alcohol abuse. At higher levels of social organization, e.g., states and nations, social capital may enhance health indirectly, such as encouraging more egalitarian patterns of political participation that in turn ensure provision of adequate health care, income support for the poor, and other social services.