Teenagers with classmates having mental illness at significantly greater risk of psychiatric diagnosis later in life: JAMA

Previous studies have indicated the possibility of mental disorders being transmitted within social networks. However, these studies often lacked broad epidemiologic evidence that spans a wide range of mental disorders. To address this gap, researchers conducted an extensive analysis of Finnish adolescents, linking demographic, health, and educational data. The objective was to determine whether exposure to classmates diagnosed with mental disorders in the ninth grade is associated with an increased risk of developing a mental disorder later in life.

The study included data on all Finnish citizens born between January 1, 1985, and December 31, 1997. Participants were followed from approximately age 16 (the end of ninth grade) until they were diagnosed with a mental disorder, emigrated, died, or until December 31, 2019. The exposure measured was having one or more classmates diagnosed with a mental disorder in ninth grade. The main outcome was being diagnosed with a mental disorder during the follow-up period.

• The study cohort consisted of 713,809 individuals, with a median age of 16.1 years at the start of follow-up, and 50.4% were males.

• Of these, 47,433 had a mental disorder diagnosis by ninth grade. Among the remaining 666,376 individuals, 167,227 (25.1%) were diagnosed with a mental disorder during the follow-up period, which encompassed 7.3 million person-years.

• Having one diagnosed classmate did not significantly increase the risk (HR, 1.01; 95% CI, 1.00-1.02).

• Having more than one diagnosed classmate increased the risk by 5% (HR, 1.05; 95% CI, 1.04-1.06).

• The risk was highest during the first year of follow-up:

• A 9% increase for one diagnosed classmate (HR, 1.09; 95% CI, 1.04-1.14).

• An 18% increase for more than one diagnosed classmate (HR, 1.18; 95% CI, 1.13-1.24).

• The risk was particularly pronounced for mood, anxiety, and eating disorders. These associations persisted even after adjusting for parental, school-level, and area-level confounders.

The study suggests that mental disorders might be spread within adolescent peer networks. This potential transmission could be due to several factors, including shared environmental influences, social learning, and emotional contagion. The findings underscore the importance of addressing mental health within school settings and peer groups. This study highlights the potential for mental disorders to be transmitted within adolescent social networks, emphasizing the need for targeted interventions and further research into the mechanisms of such transmission.

Reference:

Alho, J., Gutvilig, M., Niemi, R., Komulainen, K., Böckerman, P., Webb, R. T., Elovainio, M., & Hakulinen, C. (2024). Transmission of mental disorders in adolescent peer networks. JAMA Psychiatry (Chicago, Ill.). https://doi.org/10.1001/jamapsychiatry.2024.1126