You have turned up for your annual medical checkup. The doctor has taken your blood pressure, inquired about your diet and exercise patterns, and asked whether you smoke. Then come some rather pointed questions about your social life: Do you have many friends? Do you socialize? Which groups do you belong to? How diverse are they? How important are these groups to you?

Even though these questions are unexpected, you go through the long list of your active memberships: your book club, volleyball team, hiking group, work colleagues, and so on. Your doctor congratulates you and says that you are doing exactly the right things. You even learn that because you belong to so many social groups you should not worry if you skip your gym visit every now and then.

This exam, of course, is not how doctor visits typically go. Checkups usually end after the medical tests and a cursory exchange of pleasantries. But they shouldn’t end there.

Belonging to social groups and networks appears to be an important predictor of health—just as important as diet and exercise. This point is demonstrated by a study of 655 stroke patients reported in 2005 by Bernadette Boden-Albala, professor of sociomedical sciences and neurology at Columbia University, and her colleagues. Patients who were socially isolated were nearly twice as likely to have another stroke within five years as were those with meaningful social relationships. In fact, being cut off from others appeared to put people at far greater risk of another stroke than traditional factors such as having coronary artery disease or being physically inactive (each of which increased the likelihood of a second stroke by about 30 percent).

Such effects are not restricted to those who have a significant health problem. In a 2008 study epidemiologists and health researchers Karen Ertel, Maria Glymour and Lisa Berkman of the Harvard School of Public Health tracked 16,638 elderly Americans over a period of six years. The findings, published in the American Journal of Public Health, revealed significantly less memory loss in those who were more socially integrated and active.

Using an even more prosaic health indicator, a 2003 study by Carnegie Mellon University psychologist Sheldon Cohen and his colleagues showed that a diverse social network made people less susceptible to the common cold. Their work, published in Psychological Science, indicated that the least sociable people in their sample were twice as likely to get colds as those who were the most sociable—even though the more sociable people were probably exposed to many more germs.

Such discoveries take us beyond the old debate about body-mind dualism, which explores the nature of the link between physical and mental health (soma and psyche). There is now compelling evidence that the health risk of social isolation is comparable to the risks of smoking, high blood pressure and obesity, even after controlling for other variables known to affect health.

Eggs in Many Baskets
A body of recent research shows that belonging to multiple social groups is particularly critical in shielding people from the health hazards of important life changes. Consider the marathon runner whose injury prevents her from ever running again. Anyone might be devastated by such an injury, but the consequences are greater for a person who defines herself exclusively in terms of being a runner. Likewise, think of the workaholic who never has time for his family or friends and therefore finds adjustment to retirement particularly difficult.

We hypothesize that it is best not to have all of your eggs (social identities) in one basket in case misfortune strikes. It is better, research suggests, to spread your metaphorical eggs around a number of baskets (that is, to have multiple social identities) so that the loss of one still leaves you with others.

Three of us (Haslam, Haslam and Jetten) recently examined this notion in a study we conducted with other clinical and social psychologists—Abigail Holmes, W. Huw Williams and Aarti Iyer—at the University of Exeter in England. In the study, published in 2008 in Neuropsychological Rehabilitation, we examined the changing circumstances of 53 people who had recently suffered a stroke. Life satisfaction after the stroke was much higher for those who had belonged to more social groups before their stroke. Further analysis suggested the reason for this finding was that stroke patients who had previously belonged to a lot of groups had a bigger social support network to fall back on. This was especially critical for those who had incurred the most cognitive losses (problems with directions, forgetting names, having trouble making up their mind). Patients who saw themselves as more damaged in this way tended to describe a lower quality of life, in part because these cognitive losses made it harder for them to maintain their social relationships—stripping them of the support group life had provided.

In another study that Jetten and S. A. Haslam recently published in the British Journal of Social Psychology with social psychologists Iyer, Dimitrios Tsivrikos and Tom Postmes, we monitored first-year university students over a period of four months, beginning two months before they enrolled in school and ending two months after. A key question for us was whether we could predict which individuals were most likely to embrace their new identities as university students. As in our stroke study, one of the best predictors of healthy adjustment was the number of groups that each student had belonged to before starting school. Those who had belonged to more groups in the past had lower levels of depression, even after adjusting for other factors that could influence this transition—including uncertainty about college, the availability of social support, and academic obstacles.

Can Groups Also Bring Us Down?
So do groups always make us healthier? Can they also have a negative influence, perhaps when there is a lot of internal conflict in our group? What if our group is marginalized and stigmatized by society at large? Do we feel stronger when the groups with which we identify are strong but embattled when our groups are not respected or fail to achieve?

Group failure has been found to have one of two outcomes: sometimes people distance themselves from the group and report lower levels of group identification, but often their affiliation grows stronger and they feel greater group solidarity. And people are remarkably creative in explaining away group failure, as when they root for teams that always lose. One of us (Branscombe), along with psychologist Daniel L. Wann of Murray State University, looked at baseball and basketball fans in the U.S. and found that their degree of team identification bore no relation to the team’s success or failure. For the die-hard fans—for whom the team was central to their sense of who they were—there was no question of doing anything other than sticking with the team through thick and thin.

What about membership in a group that experiences discrimination and devaluation? Again, people can take one of two routes: either distancing themselves from the group or emphasizing their commitment to it.

This point emerges clearly from a study that Branscombe conducted at the University of Kansas with social psychologists Michael T. Schmitt and Richard D. Harvey, published in 1999 in the Journal of Personality and Social Psychology. African-Americans who felt they had been the targets of racial discrimination reported lower levels of well-being—yet at the same time, the more they felt discriminated against, the more tightly they held on to their racial identity. What was particularly interesting was that those who identified more strongly as African-American in response to perceived racial discrimination experienced better psychological well-being than those who felt discriminated against yet identified less strongly with their racial group.

Similar findings also emerge from more recent studies by Branscombe and her colleagues of women, the elderly and minority cultural groups. Feeling discriminated against has the direct effect of compromising individuals’ well-being. At the same time, people are found to cope better with prejudice, and to feel more able to resist it, if they embrace their group identity rather than denying it. Such results confirm that social groups can be the source of suffering, if they attract discrimination but in addition can be the means of dealing effectively with the slings and arrows of that very discrimination.

A similar conclusion was reached by Stephen D. Reicher, a social psychologist at the University of St. Andrews in Scotland, and S. A. Haslam on the basis of findings from their BBC Prison Study [see “The Psychology of Tyranny”; Scientific American Mind, October 2005]. In this research, male volunteers were randomly assigned to one of two groups, as “prisoners” or “guards” in a laboratory “prison.” Over the course of eight days the prisoners were transformed from a group of dispirited individuals into a well-functioning, upbeat collective. The opposite process occurred among the guards, however. Their sense of shared identity decreased over time, associated with an increasing sense of powerlessness and depressed mood. Because the conditions of the “prison” made them socially isolated, the guards came to experience high levels of burnout.

Over time these changes in group members’ social identification were reflected not only in stated levels of stress and depression but also in physiological indicators of stress—specifically, the participants’ cortisol levels. Here again is evidence that social identities and membership in social groups [become internal to] the individual, leading to changes in basic autonomic functioning.

Real or Imagined Groups?
To answer the question of why identities have a positive effect on health, it helps to examine what happens to a person when social identity is impaired or no longer functioning as it should. This is how many neuropsychologists work: they attempt to understand a particular process by looking at what happens when it breaks down.

A recent study that Haslam, Haslam and Jetten conducted at the University of Exeter, together with clinical psychologists Cara Pugliese and James Tonks, examined this issue in a group of people with dementia. This research will soon be published in the Journal of Clinical and Experimental Neuropsychology. We started with the assumption that the more severe the dementia, the less people would be able to remember details of their past lives (that is, what they used to be and how they interacted with others), leading to a reduction in overall health. Indeed, our results showed that people with early signs of dementia experienced more health problems than those whose memories were largely intact. Surprisingly, though, we found no difference between the reported health of participants in the early stages of dementia and those with more advanced dementia. If anything, people in the latter group—who typically did not know what day of the week or even what year it was—tended to feel healthier than those whose dementia was still relatively mild.

At first, this pattern was puzzling. But further analysis showed that the people with more advanced dementia tended to indicate they belonged to more groups than did those with mild dementia. In addition, groups from the past (their community group or bridge club) were in their minds in the present; unlike those with mild dementia, those with severe dementia did not remember that they were no longer active in these groups. It was this perception of group belonging that was responsible for their surprisingly higher levels of professed well-being.

This finding is consistent with the observations of neurologist Oliver Sacks of Columbia University Medical Center, who often writes about people whose lives have remained remarkably intact in the face of severe neurological impairment. In The Man Who Mistook his Wife for a Hat (Touchstone, 1998), Sacks concludes that when appraising patients’ quality of life, it is not necessarily the severity of the disorder that matters so much as a person’s ability to maintain a coherent sense of self.

A Group a Day …
Group life and a sense of social identity have a profound influence on our general health and well-being. This finding reflects something fundamental about human nature: we are social animals who live (and have evolved to live) in groups. For humans, membership in groups is an indispensable part of who we are and what we need to be to lead rich and fulfilling lives.

Recognizing the importance of social identity opens up new thinking not only in psychology but also in sociology, economics, medicine and neuroscience. Such work has practical ramifications, too, suggesting that groups can offer a social cure. “As a rough rule of thumb,” wrote Harvard University political scientist Robert D. Putnam in his book Bowling Alone (Simon & Schuster, 2000), “if you belong to no groups but decide to join one, you cut your risk of dying over the next year in half.”

In other words, participation in group life can be like an inoculation against threats to mental and physical health. This is much cheaper than the pharmaceutical pathway, with far fewer side effects. And as a means of keeping the doctor at bay, it is also likely to prove much more enjoyable.

Note: This article was originally printed with the title, "The Social Cure."