From Scientific American:
A long lunch out with co-workers or a late-night conversation with a family member might seem like a distraction from other healthy habits, such as going to the gym or getting a good night's sleep. But more than 100 years' worth of research shows that having a healthy social life is incredibly important to staying physically healthy. Overall, social support increases survival by some 50 percent, concluded the authors behind a new meta-analysis. The benefit of friends, family and even colleagues turns out to be just as good for long-term survival as giving up a 15-cigarette-a-day smoking habit. And by the study's numbers, interpersonal social networks are more crucial to physical health than exercising or beating obesity.
“I don't think a lot of people recognize that our relationships can have a physical impact as well as emotional,” says Julianne Holt-Lunstad, an associate psychology professor at Brigham Young University and co-author of the new study, published online July 27 in PLoS Medicine. The researchers analyzed results from 148 studies—which included a total of 308,849 participants—going back to the early 20th century. Most studies assessed survival in contrast to mortality from all causes, although the authors rejected studies that focused on suicide or accidental deaths. “The findings are very exciting and show how important social relationships are for improving survival,” Kira Birditt, an assistant research professor at University of Michigan's Institute for Social Research, who was not involved in the new study, noted in an e-mail to ScientificAmerican.com.