By Rob Stein
Washington Post Staff Writer
Tuesday, December 1, 2009
Loneliness is like a disease -- and what's worse, it's contagious.
Although it may sound counterintuitive, loneliness can spread from one person to another, according to research being released Tuesday that underscores the power of one person's emotions to affect friends, family and neighbors.
The federally funded analysis of data collected from more than 4,000 people over 10 years found that lonely people increase the chances that someone they know will start to feel alone, and that the solitary feeling can spread one more degree of separation, causing a friend of a friend or even the sibling of a friend to feel desolate.
"Loneliness can be transmitted," said John T. Cacioppo, a University of Chicago psychologist who led the study being published in the December issue of the Journal of Personality and Social Psychology. "Loneliness is not just the property of an individual. It can be transmitted across people -- even people you don't have direct contact with."
Moreover, people who become lonely eventually move to the periphery of their social networks, becoming increasingly isolated, which can exacerbate their loneliness and affect social connectedness, the researchers found.
"No man is an island," said Nicholas A. Christakis, a professor of medicine and medical sociology at Harvard Medical School who helped conduct the research. "Something so personal as a person's emotions can have a collective existence and affect the vast fabric of humanity."
The seemingly paradoxical finding is far more than a psychological curiosity. Loneliness has been linked to a variety of medical problems, including depression, sleep problems and generally poorer physical health. Identifying some of the causes could help reduce the emotion and improve health, experts said.
"Loneliness is more than just feeling bad," said Chris Segrin, a professor of communication and health at the University of Arizona, who was not involved in the research. "It really does have consequences."
But some researchers expressed skepticism about the findings, saying the study had the same shortcoming as the earlier work and could not necessarily rule out other explanations for the apparent association.
"It is unclear whether their statistical model will 'find' social contagion in every outcome they examine because of the limitations," Jason M. Fletcher of Yale University wrote in an e-mail. He and a colleague conducted a similar analysis using data from a large federal survey to show that acne, headaches and even height could appear to be spread through social networks if not analyzed properly.
Christakis and Cacioppo defended their work, saying their statistical methods accounted for other explanations. And others hailed the work.
"I think it's an incredible piece of research," said Mark R. Leary, a professor of psychology and neuroscience at Duke University. "I don't think we anticipated that something like loneliness would cluster like this in a population. It's surprising."
Although the study did not examine how loneliness spreads, Cacioppo said other research has provided clues. People who feel lonely tend to act in negative ways toward those they do have contact with, perpetuating the behavior and the emotion, he said.
"Let's say for whatever reason -- the loss of a spouse, a divorce -- you get lonely. You then interact with other people in a more negative fashion. That puts them in a negative mood and makes them more likely to interact with other people in a negative fashion and they minimize their social ties and become lonely," Cacioppo said.
For the study, Cacioppo teamed up with Christakis and James H. Fowler, an associate professor of political science at the University of California at San Diego, who have published a series of papers and the book "Connected," based on data originally collected by the Framingham Heart Study, a long-running government-funded project that has explored a host of health issues.
The researchers used information gathered from the participants over decades, including their friendships, identities of their neighbors, co-workers and family members, and information about their emotional state. Previous studies by Christakis and Fowler concluded that obesity, the likelihood of quitting smoking, and even happiness could spread from one person to another.
Similarly, the new analysis, involving 4,793 people who were interviewed every two years between 1991 and 2001, showed that having a social connection to a lonely person increased the chances of developing feelings of loneliness. A friend of a lonely person was 52 percent more likely to develop feelings of loneliness by the time of the next interview, the analysis showed. A friend of that person was 25 percent more likely, and a friend of a friend of a friend was 15 percent more likely.
The effect was most powerful for a friend, followed by a neighbor, and was much weaker on spouses and siblings, the researchers found. Loneliness spread more easily among women than men, perhaps because women were more likely to articulate emotions, Cacioppo said.
The researchers said the effect could not be the result of lonely people being more likely to associate with other lonely people because they showed the effect over time. "It's not a birds-of-a-feather-flock-together effect," Christakis said.
The findings underscore the importance of social networks, several experts said.
"For years, physicians and researchers thought about individuals as isolated creatures," said Stanley Wasserman, who studies social networks at Indiana University. "We now know that the people you surround yourself with can have a tremendous impact on your well-being, whether it's physical or psychological."
The findings suggest that if you help "the people on the margins of the network, you help not only them but help stabilize the whole network ," Christakis said.