Abstract
Importance
Previous research indicates that mental disorders may be transmitted from one individual to another within social networks. However, there is a lack of population-based epidemiological evidence that pertains to the full range of mental disorders.
Objective
To examine whether having classmates with a mental disorder diagnosis in the ninth grade of comprehensive school is associated with later risk of being diagnosed with a mental disorder.
Design
Cohort members were followed from August 1 in the year they completed ninth grade (around age 16) until a diagnosis of mental disorder, emigration, death, or December 31, 2019, whichever occurred first.
Setting
Population-based registry study.
Participants
Data of all Finnish citizens born between January 1, 1985 and December 31, 1997 whose demographic, health, and school information were linked from nationwide registers.
Exposure
The exposure was one or more individuals diagnosed with a mental disorder in the same school class in the ninth grade.
Main Outcomes and Measures
Being diagnosed with a mental disorder during follow-up.
Results
Among the 713 809 cohort members (50.4% of whom were males), 47 433 had a mental disorder diagnosis by the ninth grade. Of the remaining 666 376 cohort members, 167 227 persons (25.1%) received a mental disorder diagnosis during follow-up (7 324 958 person-years). A weak dose-response association was found, with no significant increase in later risk of being diagnosed with one diagnosed classmate (HR=1.01, 95% CI 1.00–1.02), but a 5% increase with more than one diagnosed classmate (HR=1.05, 95% CI 1.04–1.06). The risk was not proportional over time but was highest during the first year of follow-up, showing a 9% increase for one diagnosed classmate (HR=1.09, 95% CI 1.04–1.14), and an 18% increase for more than one diagnosed classmate (HR=1.18, 95% CI 1.13–1.24). Of the examined mental disorders, the association was strongest for mood, anxiety, and eating disorders. These associations persisted after adjusting for an array of parental, school-level, and area-level confounders.
Conclusions and Relevance
Mental disorders might be transmitted within adolescent peer networks. More research is required to elucidate the mechanisms underlying the possible transmission of mental disorders.
Previous research indicates that mental disorders may be transmitted from one individual to another within social networks. However, there is a lack of population-based epidemiological evidence that pertains to the full range of mental disorders.
Objective
To examine whether having classmates with a mental disorder diagnosis in the ninth grade of comprehensive school is associated with later risk of being diagnosed with a mental disorder.
Design
Cohort members were followed from August 1 in the year they completed ninth grade (around age 16) until a diagnosis of mental disorder, emigration, death, or December 31, 2019, whichever occurred first.
Setting
Population-based registry study.
Participants
Data of all Finnish citizens born between January 1, 1985 and December 31, 1997 whose demographic, health, and school information were linked from nationwide registers.
Exposure
The exposure was one or more individuals diagnosed with a mental disorder in the same school class in the ninth grade.
Main Outcomes and Measures
Being diagnosed with a mental disorder during follow-up.
Results
Among the 713 809 cohort members (50.4% of whom were males), 47 433 had a mental disorder diagnosis by the ninth grade. Of the remaining 666 376 cohort members, 167 227 persons (25.1%) received a mental disorder diagnosis during follow-up (7 324 958 person-years). A weak dose-response association was found, with no significant increase in later risk of being diagnosed with one diagnosed classmate (HR=1.01, 95% CI 1.00–1.02), but a 5% increase with more than one diagnosed classmate (HR=1.05, 95% CI 1.04–1.06). The risk was not proportional over time but was highest during the first year of follow-up, showing a 9% increase for one diagnosed classmate (HR=1.09, 95% CI 1.04–1.14), and an 18% increase for more than one diagnosed classmate (HR=1.18, 95% CI 1.13–1.24). Of the examined mental disorders, the association was strongest for mood, anxiety, and eating disorders. These associations persisted after adjusting for an array of parental, school-level, and area-level confounders.
Conclusions and Relevance
Mental disorders might be transmitted within adolescent peer networks. More research is required to elucidate the mechanisms underlying the possible transmission of mental disorders.
| Original language | English |
|---|---|
| Journal | JAMA Psychiatry |
| DOIs | |
| Publication status | Published - 22 May 2024 |