A study examines the spread of happiness through social networks.
This is the VOA Special English Health Report.
What makes people happier: money or having happy friends and neighbors? Researchers from Harvard University and the University of California, San Diego, have found an answer as part of a study.
Nicholas Christakis and James Fowler based the study on the emotional health of almost 5,000 people. They used information gathered over a period of 20 years, until 2003, in the Framingham Heart Study. That study began 60 years ago in Framingham, Massachusetts, to learn more about the risks of heart attack and stroke.
The new study found that friends of happy people had a greater chance of being happy themselves. And the smaller the physical distance between friends, the larger the effect they had on each other's happiness.
For example, a person was 20 percent more likely to feel happy if a friend living within 1.5 kilometers was also happy. Having a happy neighbor who lived next door increased an individual's chance of being happy by 34 percent. The effects of friends' happiness lasted for up to a year.
The researchers found that happiness really is contagious. Sadness also spread among friends, but not as much as happiness.
People removed by as much as 3 degrees of separation still had an effect on a person's happiness. 3 degrees of separation means the friend of a friend of a friend.
The study showed that having an extra 5,000 dollars increased a person's chances of becoming happier by about 2 percent. But the researchers found that the influence of a friend of a friend of a friend can be greater than that.
Another finding is that people who are married or work together do not have as much of an effect on happiness as friends do.
The findings appeared in the British Medical Journal. The National Institute on Aging in the United States helped pay for the study.
The study is described as the first to demonstrate the indirect spread of happiness. In other words, that your emotions can be affected by someone you do not directly know.
Earlier studies by the two researchers described the effects of social networks on obesity and efforts to stop smoking. The new study shows that happiness spreads through social networks like an emotional virus -- a virus people would be happy to catch.
And that's the VOA Special English Health Report, written by Brianna Blake. Transcripts, MP3s and podcasts of our reports are at voaspecialenglish.com. I'm Steve Ember.
contagious: tending to spread from person to person（传染的）