Smokers who fail to kick the habit are not only hurting their bodies but may also be missing a chance to make new friends or, in some cases, keep old ones, according to new research.

Researchers report in The New England Journal of Medicine (NEJM) that an analysis of more than 12,000 smokers (and their friends, families and colleagues) over a 30-year period shows that attempting to quit smoking can serve as a people magnet by becoming a phenomenon among social groups, like a gaggle of college students or co-workers at a small firm.

According to the study, quitting often involves networks of people who spread the word (and behavior) to other cliques with whom they interact. "In a deep way, there's an association between you quitting and the quitting of people that are two to three degrees away from you," says study co-author Nicholas Christakis, a professor of health care policy at Harvard Medical School. "People you don't know personally, their actions ripple through the network and affect you."

Christakis says the effect triggers "quitting cascades" analogous to lights going out down the line on a power grid until ultimately it goes dark. The parts of the grid that are not affected by the loss of power, as in an actual blackout, are usually those on the fringes of the web—in a quitting cascade, it is those who continue to smoke.

Richard Suzman, director of the division of behavioral and social research at the National Institute on Aging in Bethesda, Md., said the study sheds light on ways to help smokers and other addicts break their habits. "If decisions to quit cascade through social networks," he said in a statement, "then this study has provided public health campaigns a powerful new methodology with which to influence behaviors."

Christakis and colleague James Fowler, an associate professor of political science at the University of California, San Diego, used data from subjects of the Framingham Heart Study, putting together a network consisting of 12,067 people, with each person being connected to several others through familial, work or social relationships. In the detailed heart study, participants' current health—including smoking status—and social connections were updated every four years, making the data set ideal for the analysis on smoking behavior.

Those with connections to a lot of other people in the study would find themselves at the center of large social clusters. Christakis notes that at the beginning of the study, smokers and nonsmokers were just as likely to be one of these central figures, but as smoking became less and less popular, smokers moved to the periphery of these webs, whereas people who had stopped smoking (or had never started) had more connections.

Fowler notes that when looking at the data, he was shocked by how clearly the pattern of smokers moving to the outside of social circles appeared. "It's not just that the [smokers are] less popular," Christakis adds, "it's that their friends are less popular, too."

Researchers found that, unsurprisingly, spouses have the most influence on another person's smoking behavior. If a partner kicked the habit, there was a 67 percent chance their significant other would, as well. Friends were roughly half as influential; and if a person's sibling quit, they were only 25 percent likely to be inspired to drop the habit.

The scientists found that people with at least some college education were found to be more helpful partners in the quitting process as well as more easily influenced by others to toss their smokes. Christakis points out that past studies showed that people in higher socioeconomic classes were the first to embrace social trends—one of those, ironically, being smoking in the early 20th century.

One of the goals of an education, says co-author Fowler, is to make people more receptive to social norms. "Education helps people to come together and coordinate on a particular project," he says. "Here the project is health behaviors—specifically smoking."

In an editorial accompanying the study in the (NEJM), Steven Schroeder, a professor of health and health care at the University of California, San Francisco, warned about the marginalization of stalwart puffers. "A risk of the marginalization of smoking is that it further isolates the group of people with the highest rates of smoking—persons with mental illness, problems with substance abuse or both," he wrote. "These people are already stigmatized by their underlying psychiatric condition. Adding the further burden of the stigma associated with smoking makes it even harder for them to achieve the wellness that they and their families seek."