A study, published in JAMA Psychiatry, found that ninth-grade students with friends who had a mental disorder were more likely to develop one themselves later. This link remained even when considering parental factors and home addresses.
Researchers from the University of Helsinki in Finland analysed data from over 710,000 Finnish students from 860 high schools. They discovered that about 47,000 students had a mental disorder by ninth grade, and another 167,000 (25% of the total) were diagnosed later in life.
The study showed a 5% increased risk of developing a mental disorder if a student had more than one classmate with a diagnosis. This risk was higher in the first year after exposure: 9% for one diagnosed classmate and 18% for more than one.
The highest risks were for mood, anxiety, and eating disorders.
Michaela James, a mental health researcher at Swansea University, noted a rise in mental health issues among young people, with emotional difficulties affecting up to 29% of children by 2021-2022. She emphasised that this increase is part of broader societal issues, not just because of peer influence.
The researchers proposed that mental disorders might spread through normalisation, where awareness and acceptance of these conditions grow in social networks. They also suggested direct influence among peers for disorders like depression and eating disorders.
The study highlights the importance of addressing peer influences in mental health interventions to reduce the burden of these disorders. Further research is needed to understand how and why these associations occur.