Researchers say bad vibes are contagious among teens.

The more sad friends your teen has, the more likely they are to be sad themselves, according to a new study from the UK.

But gladly, they also found happiness is contagious among adolescents too.

While both good and bad moods can spread easily, good moods are contagious enough to push people out of depression, while spreading bad moods does not also spread depression, the study says.

The researchers say understanding that mood can spread socially is important for public health policy and for the design of programs to tackle depression in adolescents.

The paper is accessible here.