According to the Washington Post, recent research on social networks has shown that loneliness can be 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.

Further…

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.

According to sociologists, these results demonstrate that even individuals’ emotions have social significance:

“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.”

And…

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.