between social network structure and health outcomes. Thus, aspects of social networks ranging from structure to function are related to mortality, morbidity, cognitive and physical function, and a range of health behaviors.

As with other factors considered in this volume, while associations between social ties and mortality and health may be strong, it is often difficult to be sure of the causal direction. People who are social isolates may differ from those who are highly socially integrated in many ways. Some of these differences may also be related to their health. In some cases, poor health can be linked to social withdrawal.

The question addressed in this chapter is whether international differences in the distribution of social networks and social support, and the risks related to them, might play a role in the divergence in life expectancy among countries. To answer this question, this chapter first takes a closer look at the pathways by which social networks can affect health and mortality and the evidence for these linkages. It then examines how social networks in the United States compare with those in other countries and considers the evidence that those differences play a role in the divergence in life expectancy trends.

PATHWAYS LINKING SOCIAL NETWORKS TO HEALTH AND MORTALITY

There are a number of mediating pathways by which aspects of social networks might plausibly impact health. Most obviously, the structure of network ties influences health via the provision of many kinds of support, from financial to instrumental and emotional (Berkman and Glass, 2000). Support is often transactional in nature, potentially involving giving as well as receiving, and occurs within a normative framework of exchange over the life course that may vary across countries and cultures. Some exchanges improve access to resources and material goods. For instance, social networks have been shown to be associated with an individual’s likelihood of getting a job (Granovetter, 2003). Other types of support, such as emotional support, may impact health by reducing physiological stress responses. Social networks can also impact health through social influence whereby individuals obtain normative guidance about behaviors. Finally, negative interactions leading to conflict, abuse, or neglect can have powerful impacts on subsequent health outcomes via a number of behavioral and biological pathways.

Linking the kinds of social interactions described above to health outcomes logically requires a set of pathways by which the effects of social interaction affect health. These can be pathways that link social interaction to behaviors, psychological states, or more directly to physiological responses tied to health. Previous research has linked aspects of social



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