Happiness, not depression, is contagious, a new study says.

By Liz Steelman
Updated August 19, 2015
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If your friend's suffering from a cold, it might be a good idea to stay at arm's length for awhile. But if he or she is suffering from depression, there's no reason to stay away—in fact, sticking around might just be the best thing you can do. According to new research from the University of Warwick, having friends who suffer from depression doesn’t affect your mental health, but actually increases the chances of the depressed person's recovery.

For the study, published in Proceedings of the Royal Society B, researchers used a mathematical model similar to how infectious diseases are tracked. Using responses of 2,000 U.S. high school students from The National Longitudinal Study of Adolescent to Adult Health, participants were classified as having either a “low mood,” displaying symptoms associated with clinical depression, or a “healthy mood."

They found that the teenagers who had five or more healthy friends were half as likely to be depressed as those with no healthy friends. And if a teenager was classified with a “low mood,” but had 10 or more healthy friends, the chance of recovery in six to 12 months doubled.

“Depression has been associated with social withdrawal, and so depressed individuals would be expected to exert less social influence than adolescents with healthy mood,” explains Hill in the study. “However, each individual may need sufficient exposure to others with a healthy mood in order to stay well, or become well if depressed.”

This research can decrease stigma in those suffering from depression by increasing understanding that it is not contagious, but that social interaction and friendships is a vital factor in recovery.

"Our results suggest that promotion of any friendship between adolescents can reduce depression since having depressed friends does not put them at risk, but having healthy friends is both protective and curative," lead researcher Edward Hill said in a statement.