Using data from Finnish population-based registers, the authors found that students aged around 16 who had classmates with diagnoses of mental disorder received more diagnoses of mental disorder (especially) during the following year. The relationship was detected for some disorders such as mood disorders, but not for others such as substance use disorders. 

This study has several strengths. Firstly, the use of population-based registers provides a large amount of data, as they cover the whole of Finland, unlike conventional studies that rely on often small and unrepresentative samples. Moreover, to counteract the natural tendency we all have to associate with people similar to ourselves, the authors chose ‘class’ as the social network of study, and ‘class’ had not been chosen by the students but imposed by the institutions. 

There is a possibility that the results are influenced by variables not coded in the records, although this possibility is small because the authors took into account the student's specific school, as well as a relatively long list of demographic and socio-economic variables. 

It is important to note that this result does not necessarily imply a deterioration in mental health, but could even be a positive effect. For example, it could be that having classmates with diagnoses of mental disorders contributes to reducing the stigma associated with these disorders. As a result, it is possible that students who subsequently developed mental disorders felt more comfortable seeking help from the health care system.This effect would be very positive, considering that delaying help-seeking worsens the long-term prognosis.

The study aims to measure the risk of being diagnosed with a mental disorder when there are one or more classmates (in what would correspond to the first year of high school in Spain) who are already diagnosed. It is an ambitious and well-designed population-based research that collects data from more than 700,000 citizens over 18 years and until 2019. The results are significant, although the risk rates are low, and explain them by an increased awareness of distress in adolescents who were already suffering without being diagnosed, by the environmental influence on the most susceptible or by the ‘emotional contagion’ that can occur in close relationships.

The influence of the social context on the expression of mental distress is a particularly important aspect in adolescence, when identifications and differences with people in the environment are key in the personal development of young people. This research highlights this in the case of classmates and just ends in 2019, before the confinement due to the covid-19 pandemic and the popularisation of some networks such as TikTok. Since then, and in the context of these social changes, adolescents give evidence of their discomfort through behaviours that are more easily ascribed as ‘mental disorders’, an issue that has to make us think about what educational, family and environmental measures we can take, beyond the purely psychological or psychiatric ones.