Happiness: It Really Is Contagious

Turns out, misery may not love company — but happiness does, research suggests.

A new study by researchers at Harvard University and the University of California, San Diego documents how happiness spreads through social networks.

They found that when a person becomes happy, a friend living close by has a 25 percent higher chance of becoming happy themselves. A spouse experiences an 8 percent increased chance and for next-door neighbors, it's 34 percent.

"Everyday interactions we have with other people are definitely contagious, in terms of happiness," says Nicholas Christakis, a professor at Harvard Medical School and an author of the study.

Perhaps more surprising, Christakis says, is that the effect extends beyond the people we come into contact with. When one person becomes happy, the social network effect can spread up to 3 degrees — reaching friends of friends.

To study the spread of emotion, the researchers plotted out the social connections of about 5,000 individuals enrolled in the ongoing Framingham Heart Study.

On three separate occasions between 1984 and 2003, the participants filled out a questionnaire designed by the Center for Epidemiological Studies to assess depression and emotional health.

To measure happiness, Christakis relied on people's answers to four questions in the survey, including: "How often during the past week would you say: I enjoyed life? I felt hopeful about the future?"

When he and his colleagues plotted out how the happy and unhappy participants were connected in social space, an interesting picture emerged.

"We find that people at the center of the social network tend to be happier," says co-author James Fowler, a political science professor at U.C. San Diego.

Imagine a birds-eye view of a party: "You may see some people in quiet corners talking one-on-one," Fowler says. Others would be at the center of the room having conversations with lots of people. According to the study findings, those in the center would be among the happiest.

"We think the reason why is because those in the center are more susceptible to the waves of happiness that spread throughout the network," Fowler explains.

Of course, it's true that emotions can be fleeting; happiness is elusive and sometimes it's situational. For these reasons, emotional states are difficult to measure, says Robert Provine, a professor of psychology at the University of Maryland, Baltimore County. "There are lots of challenges."

Nonetheless, Provine, who has studied the contagion of laughter, says this study is impressive in showing that moods can be contagious, too.

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