If you're feeling great today, you may end up inadvertently spreading the joy to someone you don't even know.

This network from 2000, colored for average mood, shows yellow as happy, blue as sad, and green as in-between.

New research shows that in a social network, happiness spreads among people up to three degrees removed from one another. That means when you feel happy, a friend of a friend of a friend has a slightly higher likelihood of feeling happy too.

The lesson is that taking control of your own happiness can positively affect others, says James Fowler, co-author of the study and professor of political science at the University of California in San Diego.

"We get this chain reaction in happiness that I think increases the stakes in terms of us trying to shape our own moods to make sure we have a positive impact on people we know and love," he said. Watch more on how happiness spreads »

Sadness also spreads in a network, but not as quickly, the researchers found. Each happy friend increases your own chance of being happy by 9 percent, whereas each unhappy friend decreases it by 7 percent. This reflects the total effect of all social contacts.

When framing the question differently, the study found that you are 15 percent more likely to be happy if a direct connection is happy, 10 percent if the friend of a friend is happy, and 6 percent if it's a friend of a friend of a friend.

The study, published in the British Medical Journal, used data from the Framingham Heart Study to recreate a network of 4,739. Fowler and co-author Dr. Nicholas Christakis of Harvard Medical School charted friends, spouses and siblings in the network, and used their self-reported happiness ratings from 1983 to 2003.

http://www.cnn.com/2008/HEALTH/12/05/happiness.social.network/index.html