Research shows that happiness spreads through social groups

May 12, 2009

NIA-funded researchers have found that happiness is not an isolated phenomenon, unique to an individual, but rather spreads through social networks. Using data from the Framingham Heart Study, Drs. Nicholas Christakis of Harvard Medical School and James Fowler of the University of California, San Diego examined how social ties influence individuals’ mood and sense of well-being. They found that people who are surrounded by happy people are more likely to be happy themselves.

The researchers looked at the happiness of nearly 5,000 individuals in the Framingham cohort during a period of 20 years. They found that one person’s happiness triggers a chain reaction that benefits not only their friends, but their friends’ friends, and their friends’ friends’ friends, with the effect lasting for up to a year.

The effects are limited by both time and space. The closer a friend lives to a person, the stronger the effect. As distance increases, the effect decreases. This explains why friends who are next-door neighbors have an effect, but those who live around the block do not. Interestingly, the effects did not apply to co-workers and were stronger between same-sex than between opposite-sex pairs.

This is the third major network analysis by these researchers that shows how social context affects health. The two previous studies, published in the New England Journal of Medicine, described the social network effects in obesity and smoking cessation.


Fowler, J.H., and Christakis, N.A. Dynamic spread of happiness in a large social network: longitudinal analysis over 20 years in the Framingham Heart Study. BMJ. 2008 Dec 4. 337:a2338.

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