Wednesday, September 16, 2009

Is health contagious?

This is a guest post by Ethan Segal, MD. If you're interested in submitting a guest post, please contact me.

There is an interesting article in the NYtimes magazine, "Is Happiness Catching?," Is Happiness Catching? - The article deals with the phenomenon of "social contagion, " that behaviors, like overeating or smoking can spread through friendship networks. Two social scientists, Christakis and Fowler, published a study in 2007, that analyzed the friendships in the thousands of study participants in the Framingham Heart Study, the landmark study on health and heart disease. They found that good behaviors-like quitting smoking or staying slender or being happy-pass from friend to friend almost as if they were contagious viruses. The same was true of bad behaviors-clusters of friends appeared to "infect" each other with obesity, unhappiness, and smoking. There was a lot of criticism of the study when it was published regarding confounding variables such as the influences of environment (a McDonald's opens in a neighboorhood that makes the social group fat), or that the results were due to "birds of a feather flock together."

While I don't think the notion that social reinforcement influences behavior is an earth-shattering hypothesis, but some of their specific findings were provoking. For instance, if an individual became fat, not just did it make it more likely that their best friend became fat, but that third and fourth degree friends also were likely to soon gain weight. Also, if an individual moved outside the area, the social network still had its effect, arguing against an environmental effect. That means if you gain weight, your friend of a friend who you dont really talk too that much might also gain weight because of you. The authors themselves talk about their findings raising personal responsibility, for instance, the author says after he saw the results it prompted him to lose five pounds and listen to happy music when he got home to his family. He might influence not only his family, but maybe a friend of a friend's family as well. Another interesting point was the effect of publishing your personal efforts to lose weight or quit smoking on your Facebook account. Public health could potentially benefit from using such social networks to influence health behaviors.

This guest post was written by Ethan Segal, MD. Ethan Segal earned a BA from Amherst College and a MD from Tufts University School of Medicine. He is currently working freelance as a medical writer and applying to residency programs for July 2010. He can be reached at Ethan.Segal(at)

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