Smoking Is Addictive, But Quitting Is Contagious

Over the last 30 years, the number of smokers in the United States has steadily decreased—a tribute to the efforts of public-health workers everywhere. And while this fact is unarguable, less obvious are the social and cultural forces that lead an individual to kick the habit. In fact, when someone crumples that last empty pack of his favorite unfiltered brand and vows to never buy another, he might not realize that he is less like the heroic individual grasping his own boot straps and more like a single bird whose sudden left turn is just one speck in the larger flock.

Courtesy James Fowler, UC San Diego

What a difference 30 years can make. Yellow nodes indicate smokers (the larger the node, the heavier the smoker), whereas green nodes indicate nonsmokers. Arrows represent social ties, orange for friends and spouses and purple for family members. Note how smokers have not only decreased in numbers but have shifted to the periphery of social groups.

These are the findings of a massive longitudinal study spanning 32 years: people quit smoking in droves. Through reconstructing the social network of 12,067 individuals, researchers from HMS and the University of California, San Diego, have discovered that smoking cessation occurs in network clusters and is hardly the isolated decision it might feel like to the individual quitter.

“We’ve found that when you analyze large social networks, entire pockets of people who might not know each other all quit smoking at once,” said Nicholas Christakis, an HMS professor of medical sociology in the Department of Health Care Policy, who, along with U.C.-San Diego researcher James Fowler, authored the study. “So if there’s a change in the zeitgeist of this social network, like a cultural shift, a whole group of people who are connected, but who might not know each other, all quit together.” The study appears in the May 22 issue of The New England Journal of Medicine.

Dominoes
Over the last few years, Christakis, who is also a professor of sociology in the Faculty of Arts and Sciences at Harvard University, and Fowler have been analyzing data from the Framingham Heart Study, recreating the social patterns contained within the data to see how health correlates with an individual’s social network.

The researchers derived information from archived, handwritten administrative tracking sheets dating back to 1971. All family changes for each study participant, such as birth, marriage, death, and divorce, were recorded. In addition, participants had also listed contact information for their closest friends as well as coworkers and neighbors. Coincidentally, many of these friends and coworkers were also study participants. Focusing on 5,124 individuals, Christakis and Fowler observed a total of 53,228 social, familial, and professional ties.

Last year, they reported on the spread of obesity through social networks. Using the same data, they analyzed smoking-cessation trends within the same population.
The first and most striking finding was the discovery that, from the larger network perspective, people quit smoking as groups and not as individuals.

“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,” said Fowler. “It’s just that there are fewer and fewer of these clusters as time goes on.”

They were able to quantify the person-to-person effects of smoking cessation among married couples, siblings, friends, and coworkers. In addition, they also discovered “quitting cascades” that advanced from person-to-person-to-person.

Christakis illustrates this point by describing a small network containing three individual smokers, persons A, B, and C. The first person, A, is friends with B, and B is friends with C, but A and C do not know each other. If C quits smoking, A’s chances of not smoking spike 30 percent, regardless of whether or not B smokes. The middle individual, it would appear, might act as a kind of “carrier” for a social norm.

Education also seems to matter. People are more influenced by the quitting behavior of others if those people are highly educated. To add a further twist, people are also more influenced by others if they themselves are more educated.

Said Christakis, “We see by this that the educated are not only more influential, but they are also more easily influenced.”

Finally, Christakis and Fowler discovered that smokers are increasingly marginalized throughout social networks.

“If you look back at 1971, smokers and nonsmokers alike were at the centers of social networks,” said Fowler. “For people running companies and having parties, smoking was irrelevant. But during the ’80s and ’90s, we saw a dramatic shift of smokers to the periphery of the social network. Contrary to what we might have thought in high school, smoking has become a supremely bad strategy for getting popular.”

Health Network
This marginalization of smokers appears to occur across all educational and economic demographics.

According to the researchers, this is an additional concern. Social marginalization leads to poor health. Smoking then is not only bad for your physical health but for your social health as well.

“What people need to understand is that because our lives are connected, our health is connected,” said Christakis.

“Policymakers have an understandable tendency to treat people as atomized individuals and to anticipate the impact of their policies accordingly,” said Duncan Watts, professor of sociology at Columbia University, who was not involved with the research. “What this study—like the authors’ previous study on obesity—points out clearly, however, is that individuals do not behave as atoms, but as part of a network. Although simple to state, the consequences of that observation are profound and will require us to fundamentally rethink our intuition about the world.”

“The culture of individualism is so strong that we sometimes forget how powerfully and silently social networks and those around us influence our health,” said Richard Suzman, director of the National Institute on Aging’s Division of Behavioral and Social Research. “If decisions to quit cascade through social networks, then this study has provided public health campaigns a powerful new methodology with which to influence behaviors.”

—David Cameron

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