Do other teens influence your teen’s mental health? What if your teen hangs out with friends who are depressed or highly anxious? Is it possible that a peer group could be contagious to developing mental illness? Does having a classmate with a mental illness lead to later psychiatric diagnoses among peers?  These are interesting questions researchers in Finland decided to study. This study is part of a larger effort to investigate the transmission of mental disorders in teens.

We know that teens are highly influenced by their peer group. There are a few survey studies that indicate mental health symptoms in teens may increase when exposed to teens with mental health problems, but no large-scale studies have been done  one reason why the Finnish researchers took this on.

Here is what the Finnish study did: They used a data base of around 700,000 000 ninth grade students born between 1985 and 1997 that had no mental disorder before the study began. Those students were followed for up to 18 years –until they had a first diagnosed mental disorder, death, emigration, or until the end of the study in 2019. The aim of the study was to see if having teen classmates in your social network was associated with later risk for mental disorders.

What they found was that over a quarter of the students were diagnosed with a mental health disorder. But the takeaway from the study was that a teen with classmates who have mental illness was at an increased risk to develop a mental illness later in life. This led to the conclusion that teens may transmit mental health problems such as depression and anxiety to each other.

Now, the increased risk was small, 3% higher for developing psychiatric diagnosis if you had a classmate with mental health problems. The risk jumped to 13% in the first year of follow up and was the highest for anxiety, mood disorders, and eating disorders. And the more people in the teen social network with mental disorders, the higher the risk.

However, this study is not saying that having a classmate with a mental health disorder will cause a teen to develop one. But it is suggesting there is an increased risk.

The study supports the idea that transmission of psychiatric disorders is possible. Who you keep company with may have an influence on your mental health now and later. Of course, we know the power of peer groups on a teen’s development, but this brings a unique aspect into that development.

Efforts need to be made to assess teen peer groups and how their influence impacts mental health. Peers can be positive influences as well, especially those with high emotional intelligence and good coping skills.