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.

Accentuating the positive
Social relationships are thought to help improve health either by buffering individuals from stressful situations or creating a norm of healthful behaviors.

"There's a pretty large literature linking social relationships to a variety of physiological processes that are linked to disease risk," Holt-Lunstad says. Social support has been linked to lower blood pressure, and a diverse collection of contacts is associated with better immune system functioning. The list continues to grow, she says, now encompassing other bodily processes such as wound healing and inflammation.

Previous research has pointed to happiness as a key to longevity. But in most of the studies reviewed in the new paper, social connections were not classified in terms of their quality, thus likely lumping negative associations in with the more positive ones. This means the benefit of positive social connections is likely to be even higher.

"Most research shows that the negative aspects of relationships can be detrimental to health," Holt-Lunstad says. But Birditt, who has also done research in the field, notes that some of her work "indicates that the influence of social relationships on mortality is nuanced and depends on the type of relationship, the quality of the relationship and the health status of the individual." A 2008 study in Social Science & Medicine that she co-authored found that people with chronic illnesses actually had a lower mortality rate if they had negative—or at least more demanding—relationships with family members. "We speculated that spouses and adult children may be nagging the person with the chronic illness to take their medication or that more demands from these ties may be a sign of greater engagement," Birditt notes.

The more, the healthier
Despite the hyperconnected era of Facebook friends and Blackberry messaging, social isolation is on the rise. More people than not report not having a single person they feel that they can confide in—up threefold from 20 years ago, the report authors noted.

"People have assumed a threshold effect" when it comes to social relationships, Holt-Lunstad says. Many researchers thought "you're at risk if you're socially isolated, but as long as you have one person, you're okay," she says.

The decades of research that Holt-Lunstad and her colleagues examined showed that in fact social support and survival operate on a continuum: "The greater the extent of the relationships, the lower the risk," she says.

The analysis also assessed what kind of studies worked best to predict a person's survival. Questionnaires that had asked participants at least a few in-depth questions about various social connections (such as, "To what extent are you participating or involved in your social network?" or "To what extent can you count on other people?") were more effective at pinpointing a person's overall risk of mortality from all causes than those that simply determined if a person was single or married or lived with at least one other person. The more nuanced questions "tap into the perception of the availability" of other people, Holt-Lunstad explains, rather than just determining if a person is co-habitating. Holt-Lunstad and her colleagues found that divvied up this way, complex social networks increased survival rates by 91 percent.

Rx: friendship
Health professionals might be better able to find people at risk if they know to look more deeply at an individual's social environment. So rather than only focusing on those who seem to be entirely socially isolated, health care workers could also encourage friendship and personal connectedness for a larger number of people—thus perhaps boosting overall population survival rates.

Some clinicians have prescribed social interaction for those who seem to be severely isolated, but that often comes in the form of a paid companion. Such a dynamic is "not always effective," Holt-Lunstad says. "A naturally occurring friendship is very different than someone who has been hired to be your buddy or your friend." Research has shown that friends "provide a sense of meaning or purpose in our lives," she says. A professional "friend" "might be able to provide some tangible resources that would be helpful, but they might not be able to provide the emotional benefits."

Likewise with digital social interactions, Holt-Lunstad says, "there are types of things you can get from an online friend, but there are other resources that you cannot." Although online connections "might be better than nothing," substituting time in front of a screen is likely not as beneficial as a phone call or face-to-face conversation.

Given the increasingly apparent importance of social well-being for physical health, standard checkup questions asked by a physician might soon include inquiries into the patient's social, family and work circles—in addition to the standard list about smoking, diet and exercise.

Although social and physical health are intimately linked, Holt-Lunstad does not see it as a purely medical issue. She suggests a range of avenues to address the social fitness of the population: from school curriculums emphasizing good social skills to city planning that reinforce community building to workplaces that accentuate human interaction.