The contagious nature of bacterial or viral infections such as strep or influenza is well understood. You’re at risk of getting the flu, for example, if someone close to you has it, because the virus can spread through droplets in the air, among other ways of transmission. But what about a person’s mental health? Can depression be contagious?

A JAMA Psychiatry the paper published earlier this year seemed to suggest so. The researchers reported that they found “an association between having peers diagnosed with a mental disorder during adolescence and an increased risk of receiving a diagnosis of a mental disorder later in life.” They suggested that among adolescents, mental health disorders could be “socially transmitted”, although their observational study could not establish any direct cause.

It makes some intuitive sense. Psychologists have studied how moods and emotions can spread from person to person. Someone who roars with laughter can be contagious in that it makes you laugh too. Similarly, seeing a friend in emotional pain can evoke feelings of despair—a phenomenon called emotional contagion.

For more than three decades, researchers have investigated whether mental health disorders may also exist INDUCED by our social environment. Studies have found mixed results regarding the extent to which friends, fellow and families“mental health can in turn affect an individual’s mental health.

The JAMA Psychiatry The study – conducted by researchers from Finland’s University of Helsinki and other institutions – analyzed nationwide registry data on 713,809 Finnish citizens born between 1985 and 1997. The research team identified individuals from schools in Finland who had been diagnosed with a mental disorder by the time they were diagnosed. in the ninth grade. They followed the rest of the cohort to record subsequent diagnoses until the end of 2019.

The study found that ninth-graders who had more than one classmate diagnosed with a mental health disorder had a 5 percent higher risk of developing a mental illness in subsequent years than students without classmates class with diagnostics. The risk was particularly high in the year immediately following exposure: students with a diagnosed classmate were 9% more likely to receive a mental health diagnosis, while students with more than one diagnosed classmate were 18% more likely to large to receive a diagnosis. The risk was greatest for mood, anxiety and eating disorders. The increased risk was observed after adjusting for a number of potential confounders at the parental, school, and regional levels, such as parental mental health, class size, and area-level unemployment rates.

These results might seem like compelling evidence for the social transmission of mental health disorders, but other researchers, such as Eiko Fried, a clinical psychologist at Leiden University in the Netherlands, suggested that the Finnish team may not have controlled for all relevant confounders. Fried grew up living in a poor neighborhood, which increases the risk of depression, as an example of confusion in an email to Darkness. “These kids end up in the same schools and in those schools you have an aggregation of depression. This now looks like social contagion, until the confounding factor – the neighborhood – is taken into account.”

The researchers controlled for neighborhood employment rates and education levels, but may not have accounted for other influential contextual factors. To the extent that these common factors are insufficiently measured, estimates of correlated outcomes risk placing causality on the wrong variable. One post on X (formerly Twitter), Fried said it might be more plausible that hidden confounders explain what’s going on, rather than social contagion.

In response to an email question that featured criticism of potentially confounding variables, the lead author of the Finnish study, Jussi Alho, emphasized the usefulness of using classrooms as a reference point, pointing to another potential influence: people’s tendency to seek or to be attracted to those who resemble themselves. “In our study, we mitigated this self-selection bias by using school grades as a proxy for social networks,” he explained. “As institutionally imposed social networks, school classes are well suited for research because they are typically not formed endogenously by individuals selecting similar others as classmates. Furthermore, school hours are arguably among the most important peer networks during childhood and adolescence, given the substantial amount of time spent with classmates.”

According to Alho and his co-authors, as they write in the paper, the strength of the Finnish study lies in the fact that the investigated social networks were not independently chosen by the research subjects. At the same time, Alho allowed that critics have a point: “We cannot fully rule out residual confounding,” he wrote in an email to Darkness“due to unmeasured or incorrectly measured covariates in our study.”

These confounding factors are a persistent problem pursuing this line of research. A 2012 study published in the journal Health Economicsfor example, it examined the mental health of college roommates in their first year, testing for possible “contagion among people who are placed together largely by chance.” The authors described the study as a natural experimentwhich they claimed could produce, in their words, “unbiased estimates” of the “causal effect”.

The researchers found “no significant overall mental health contagion and no more than small contagion effects for specific mental health measures,” such as general psychological distress, depression, and anxiety. Even in this case, however, the mild contagion effect could be attributed to unmeasured factors, such as students sharing comparable social backgrounds and education. After all, they are going to a school for which they would have been selected based on similar academic interests or extracurricular skills.

All of these possible influences make it difficult to know what is causing what. Are mental health issues spreading among people on social media? Or are other unknown factors just creating this impression?

Whatever the answer, such personal exposures can generate another type of contagion: public awareness. Generalized anxiety disorder, for example, first appeared as a diagnosis in the third edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM) in 1980. The condition causes “excessive, frequent, and unrealistic worrying about things from day to day”, appropriate Cleveland Clinic Health Library. By the time the fourth edition of the DSM and its updated diagnostic criteria for generalized anxiety disorder appeared in 1994, the disorder had “transformed from a rarely diagnosed condition to a disorder with a lifetime prevalence reaching to up to 5% in a community sample’. according to 2017 paper on the diagnostic history. Data from a 2016 Agency for Healthcare Research and Quality report on anxiety in children indicates that childhood anxiety occurs in about one in four children between the ages of 13 and 18, while the lifetime prevalence of severe anxiety disorder in that age group is 5.9 percent .

What is driving these rates is better awareness among both patients and doctors. Or, it could result from an umbrella of other factors, such as evolving diagnostic criteria and improved access to treatment. But as Alho and colleagues suggest in their paper, it may also be driven by knowledge and acceptance of mental health disorders acquired through social media. After all, exposure to a colleague with a mental disorder, the researchers noted in their study, may well help “normalize mental disorders by increasing awareness and responsiveness to diagnosis and treatment.”

Joshua Cohen is a Boston-based freelance healthcare analyst and freelance writer and author Darknesshis Cross sections column.

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