Over the past 30 years, the prevalence of smoking in the United States has decreased substantially. According to a study published in the New England Journal of Medicine, quitting smoking is heavily influenced by spouses and friends

Using a densely interconnected social network of 12,067 people who were repeatedly evaluated from 1971 to 2003 as part of the Framingham Heart Study, researchers from Harvard University and the University of California, San Diego studied the extent of person-to-person spread of smoking, as well as the extent to which groups of people quit together. They found that people who had a spouse who quit smoking were 67% less likely to smoke, while a friend who quit smoking decreased a person's chance of smoking by 36%. People with friends or co-workers who quit smoking were also less likely to smoke. The researchers concluded that smoking behavior spreads through both close and distant social ties, with groups of interconnected people quitting smoking together in clusters. In addition, the researchers found that smokers had fewer friends and were less socially well-connected, indicating increased marginalization and a negative impact on social, as well as physical, health.

In a world where social networking is enabled by technology, the findings of this study could be useful in the development of public health interventions for smoking cessation that can further reduce the prevalence of smoking and the risk of smoking-related medical conditions.