Smoking is addictive but giving up the habit is contagious, a new study has claimed.
Researchers in the United States have found that people quit puffing in droves -- in fact, the cessation occurs in network clusters and is hardly the isolated decision as it might feel like to the individual quitter.
According to the study's lead author Prof Nicholas Christakis of Harvard Medical School, "We've found that when you analyse large social networks, entire pockets of people who might not know each other all quit smoking at once.
"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."
Prof Christakis and fellow researchers at University of California reached the conclusion after analysing 12,067 people who have been taking part in Framingham heart study -- a study of the health and habits of nearly an entire town in Massachusetts -- for the past 32 years.
The data included smoking habits and, over the years, many participants gave up. At regular intervals since 1971, the participants recorded births, marriages, divorces and deaths, and listing contact information for their closest friends, co-workers and neighbours.