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Quitting Smoking Good
for Your Social Health, Too

Social-Network Study Finds Group Effects in Smoking Cessation

May 21, 2008

By Inga Kiderra

Putting down cigarettes for good can have unexpected social benefits, according to new research from Harvard and the University of California, San Diego. Smoking is bad, it turns out, not only for your physical wellbeing but for your social health, too — with smokers increasingly edged out to the margins of social circles.

Another significant finding of the study, published in the May 22 issue of the New England Journal of Medicine, is that the decision to quit appears to be taken up almost communally, with whole clusters of spouses, friends, siblings and co-workers giving up the habit at about the same time.

The researchers — Nicholas Christakis of Harvard Medical School and James Fowler of UC San Diego — analyzed changes in smoking behavior from 1971 to 2003 in a large social network of 12,067 densely interconnected people.


Smoker Nodes illustration
1971 2000

A random sample of 1000 subjects in 1971 and 2000. Yellow nodes are smokers (with the node size proportional to number of cigarettes consumed); green nodes are nonsmokers. Orange arrows denote friendship or marital ties; purple arrows, family ties. In 1971, there are many more smokers and they are dispersed throughout the social network. By 2000, there are not only fewer people smoking, but they have also been pushed to the outside of their social groups.

Courtesy James Fowler, UC San Diego.
Click for enlarged illustration.


The study follows up on research by Fowler and Christakis published last summer, also in the New England Journal of Medicine, finding that obesity is “socially contagious” — spreading from person to person in a social network so that if one becomes obese those closely connected to them have a greater chance of becoming obese themselves.

Using data from the same Framingham Heart Study (which, among other things, was the first to identify the link between smoking and cardiovascular disease), the researchers observed that smoking behaviors are subject to similar social-network effects, at two and three degrees of separation. Except that quitting smoking, they found, spread through the network not only like one domino knocking down the next, which in turn knocks down another, but also like a house of cards collapsing.

Christakis and Fowler note that their findings speak both to the power of relationships and to the efficacy of public-health campaigns to reduce smoking. While smoking remains a leading cause of preventable death, rates in the U.S. have decreased substantially.

“When you look at the entire network over this 30-year period, you see that the average size of each particular cluster of smokers remains roughly the same,” Fowler said. “It’s just that there are fewer and fewer of these clusters as time goes on.”

Observing that “entire pockets of people who might not know each other all quit smoking at once,” said Christakis, points to a cultural shift or a change in the zeitgeist. “What appears to happen is that people quit in droves.”

Generally, the researchers found, the closer the relationship between contacts, the greater the influence when one person quit smoking. When one spouse quit, for example, the other spouse’s chances of continuing to smoke decreased by 67 percent.  Among friends, the effect was 36 percent. Among co-workers in small firms, 34 percent.  Among siblings, the effect was 25 percent. Neighbors did not seem to be influenced by one another’s smoking habits.

Education played a role: Among friends who both had at least one year of college, the effect was 61 percent. The paper concludes that the educated are not only more influential, but also that they are also more easily influenced.

Surprisingly, people quit roughly in tandem, with whole groups becoming nonsmokers. Those who continued to smoke, meanwhile, formed their own “cliques” that, over time, shifted from the center of the social network to the periphery.

“In the early 1970s,” said Fowler, “it was completely irrelevant if you smoked. You could be central in your circle and be connected to lots of other people who were similarly central. You could be popular, in other words. By the 2000s, it had become highly relevant: If you smoked, you would, in some sense, be shunned.”

The reverse was also true: Once you quit, you tended to move back to a more central position among your contacts.

“We show,” Fowler said, “that this not coincidental — there seems to be a causal relationship at work.”

All of which points to possible policies for addressing other public-health concerns — like the researchers’ previous study case, obesity.

“Network phenomena,” they write, “might be exploited to spread positive health behaviors,” and targeting groups, not just individuals, might be more effective.

Yet, cautions Fowler, effective doesn’t necessarily equate with good. “Stigmatization is effective,” he said. “But is it always advisable? Social pressure comes with a cost. We see here that we have stigmatized not only smoking but smokers too. Huddling in a corner with your smoking friends is going to make it that much harder for you to stop. And we also know from other research that social isolation is detrimental to your physical health on several other levels as well.”

This research was funded by the U.S. National Institutes of Health/National Institute on Aging, a Pioneer Grant from the Robert Wood Johnson Foundation, and a contract from the National Heart, Lung, and Blood Institute to the Framingham Heart Study.


Media Contacts:
Inga Kiderra, UC San Diego, 858-822-0661
David Cameron, Harvard Medical School, 617-432-044

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