Better Health With More Friends: The Role of Social Capital in Producing Health.

This paper estimates the effect of an individual's number of friends on own health outcomes. The identification strategy exploits the panel structure of the friendship data from the National Longitudinal Study of Adolescent Health to estimate individual fixed effects in the likelihood of friendship formation and then uses the fixed effect estimates as a control function in a model relating health outcomes to number of friends. Empirical results show that having a larger number of friends improves physical and mental health and also lowers the frequency of smoking cigarettes. Specifically, making one more friend increases an individual's general health measure by 6.6% of a standard deviation. This suggests that accumulating social capital through friendship interactions is beneficial to health.