Staying socially connected may be just as important for public health as washing your hands and covering your cough. A new study suggests that feelings of loneliness can spread through social networks like the common cold. “People on the edge of the network spread their loneliness to others and then cut their ties,” says Nicholas Christakis of Harvard Medical School in Boston, a coauthor of the new study in the December Journal of Personality and Social Psychology. “It’s like the edge of a sweater: You start pulling at it and it unravels the network.” This study is the latest in a series that Christakis and James Fowler of the University of California, San Diego have conducted to see how habits and feelings move through social networks. Their earlier studies suggested that obesity, smoking and happiness are contagious.
The new study, led by John Cacioppo of the University of Chicago, found that loneliness is catching as well, possibly because lonely people don’t trust their connections and foster that mistrust in others.
Loneliness appears to be easier to catch from friends than from family, to spread more among women than men, and to be most contagious among neighbors who live within a mile of each other. The study also found that loneliness can spread to three degrees of separation, as in the studies of obesity, smoking and happiness. One lonely friend makes you 40 to 65 percent more likely to be lonely, but a lonely friend-of-a-friend increases your chances of loneliness by 14 to 36 percent. A friend-of-a-friend-of-a-friend adds between 6 and 26 percent, the study suggests.
Not all networks researchers are convinced. Jason Fletcher of the Yale School of Public Health says that the studies’ controls are not good enough to eliminate other explanations, like environmental influences or the tendency of similar people to befriend each other. Fletcher has published a study (in the same issue of the British Medical Journal that reported that happiness