Study shows certain moods are contagious

Having friends is good for your soul, and may also be good for your health. New research shows that a healthy mood spreads among friends, while depression does not.

Using data from the National Longitudinal Study of Adolescent Health, researchers from the University of Manchester and the University of Warwick in the U.K. examined how moods spread among networks of teens.

The team looked at data from over 2,000 teens in the United States. Using methods similar to those that scientists use to track the spread of infectious disease, the researchers analyzed the spread of healthy or depressed moods among each student's network of friends.

They found that having friends with a healthy mood reduces a teen's chance of developing depression, and increases the chance of recovering from depression.

"What we found is that if you have sufficient friends who are not depressed, in a healthy mood, then that can halve your probability of developing, or double your probability of recovering from, clinical depression in the six to twelve month period that the study ran over," Dr. Thomas House, a senior lecturer in applied mathematics from the University of Manchester and an author of the study, told CBS News.

But importantly, researchers found that depression does not spread.

"There's no negative effect to friendship," said House. "Your depressed friends don't put you at more risk; in fact, you can help them recover."

The study was published Tuesday in the journal Proceedings of the Royal Society B: Biological Sciences.

Depression is a major public health concern worldwide. The World Health Organization estimates that, globally, more than 350 million people of all ages suffer from depression.

House notes that while more work needs to be done on the subject, the new research suggests that promoting friendships among teens could help reduce the problem.

"As a society, if we enable friendships to develop among adolescents (for example, providing youth clubs), each adolescent is more likely to have enough friends with healthy mood to have a protective effect," House said in a statement. "This would reduce the prevalence of depression."