Using data from population-wide registers, researchers from the University of Helsinki, the Finnish Institute of Health and Welfare, the University of Jyväskylä and the University of Manchester investigated whether mental disorders can be transmitted within social networks formed by school classes .
The study is the largest and most comprehensive to date on the spread of mental disorders on social networks, and more than 700,000 ninth grade students from 860 Finnish schools have participated. The adolescents were followed from the end of ninth grade for an average of 11 years.
The researchers showed that the number of classmates diagnosed with a mental disorder was associated with an increased risk of receiving a mental disorder diagnosis in the future.
“The observed link was stronger during the first year of follow-up of the study. This is not explained by a number of factors related to parents, school and residential area. The link was more pronounced in the case of mood, anxiety and eating disorders,” says Associate Professor Christian Hakulinen of the University of Helsinki.
Research facilitated by complete Finnish records
According to Hakulinen, previous studies have shown similar results: for example, American researchers have observed signs of depressive symptoms potentially transmitted from one individual to another on social networks.
However, in previous research, social networks were usually chosen independently by the research subjects, which may result in biases in the data. Hakulinen points out that school classes are social networks well suited for research, since people typically cannot choose their classmates.
“Defining social networks and monitoring adolescents was made possible by extensive Finnish records. The findings significantly deepen our understanding of how mental health problems develop and affect other people in our social networks,” he says.
However, Hakulinen points out that the connection observed in the study is not necessarily causal. Additionally, the study did not investigate how mental disorders can potentially be transmitted between people.
“It is possible, for example, that the threshold for seeking help for mental health problems may be lowered when there are one or more people in your social network who have already sought help for their problems. Indeed, this type of normalization of diagnosis and treatment treatment can be considered a beneficial contagion of mental disorders,” says Hakulinen.
More preventive measures?
Mental disorders are a major global challenge that negatively affects individuals, society and the economy. According to Hakulinen, in recent years anxiety and mood symptoms have especially increased among young people.
Previous studies have shown that in about half of cases, mental disorders in adulthood appear when people are under 18 years old. In fact, Hakulinen highlights the importance of preventive measures and early intervention.
“When taking preventive measures, we must take into account that mental disorders can be transmitted from one adolescent to another,” says Hakulinen.
A total of 713,809 Finnish citizens born between 1985 and 1997 participated in the study. The adolescents were investigated from the end of secondary school until they received the first diagnosis of a mental disorder, moved out of the country or died. At the latest, follow-up was discontinued at the end of 2019, resulting in a mean follow-up period of 11.4 years.
The study received funding from the European Research Council (ERC) and the Finnish Research Council.