Researchers at the University of Warwick and the University of Manchester in the U.K. looked at data from 2,000 teens in the United States based on data from the National Longitudinal Study of Adolescent Health. Using methods similar to the types scientists use to track the spread of disease, they were able to see just how moods spread between the teens and their social networks.
The results showed that those who had more friends with healthy moods reduced the teen's chance of developing depression, and increased the likelihood of the teen 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," study co-author Thomas House, a senior lecturer in the School of Mathematics at the University of Manchester, told CBS News.
The researchers also learned that having friends who suffer from depression doesn’t effect the mental health of the friends surrounding them.
"There's no negative effect to friendship," House told the news outlet. "Your depressed friends don't put you at more risk. In fact, you can help them recover."
The World Health Organization estimates that more than 350 million people of all ages suffer from depression around the world.