Feeling Happy? Thank Your Friends

New research from James Fowler of UC San Diego and Nicholas Christakis of Harvard Medical School shows that happiness spreads far and wide through a social network -- traveling not just the well-known path from one person to another but even to people up to three degrees removed.

In a study that looked at the happiness of nearly 5,000 individuals over a period of 20 years, researchers found that one person's happiness triggers a chain reaction that benefits not only their friends, but their friends' friends, and their friends' friends' friends. The effect lasts for up to one year.

The flip side, interestingly, is not the case: Sadness does not spread through social networks as robustly as happiness. Happiness appears to love company more so than misery. On average, every happy friend increases your own chance of being happy by 9 percent. Each unhappy friend decreases it by 7 percent.

The research also showed that happiness loves company. Happy people tend to cluster together, and, on the surface, people with more social contacts seem generally happier. Fowler and Christakis observe, however, that what matters there is not just the total number of connections but the number of happy ones.