If there is one thing most people know about teenagers and their mental health, it is that things are getting worse. Rates of several mental health conditions are on the rise in this group, especially in the US, but also in Australia, the UK and many other European countries.
While several possible causes have been debated, further evidence has emerged for an alarming possibility that has long been suspected, but has been hard to quantify. The idea is that mental health problems can, in a way, be transmitted among groups of friends.
If this is right, it would mean our approaches to helping troubled teens with conditions such as anxiety and depression need to be re-examined. Some of the things we do could even be making things worse. So, how strong is the evidence?
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There is no shortage of other explanations proposed for young people鈥檚 worsening mental health. They include the relatively recent explosion of social media use, as well as longer-term societal changes, such as growing pressure to do well at school or changing parenting styles that may leave children less resilient.
The transmission idea doesn鈥檛 imply that mental health conditions are literally contagious, caused by bacteria or viruses. It says that when teens see one or more of their friends develop such a condition, it becomes more likely that they follow them down the same route, says at the University of Helsinki in Finland.
It has long been known that some less common mental health conditions, such as eating disorders, can spread through groups of friends. More recently, they have been shown to spread through online networks too. have also found that the two most common mental health conditions, anxiety and depression, can cluster among groups of friends. But this could be because someone who is prone to anxiety, for example, may be drawn to other anxious people.
To get around this problem, Hakulinen and his colleagues tracked the school and health records of all Finnish children who turned 16 between 2001 and 2013, to see if correlations also happened within school classes, because pupils can鈥檛 choose their classmates.
Sure enough, over the first year, if one person in a class had any mental health condition, there was a 9 per cent higher chance that their classmates would also get any such condition. Those with more than one affected classmate had an 18 per cent higher risk of being diagnosed themselves.
The effects were stronger when considering links between specific conditions: in other words, if one pupil had anxiety, others were more likely to develop anxiety. This was true for depression and eating disorders too.
As the researchers followed up with the teens, for an average of 11 years, the effects remained but got smaller if someone had more than one affected classmate and disappeared if they had just one affected classmate.
An important caveat is that this kind of study can only show correlations, not causation. Something else could be causing all children in a class to be at risk of worse mental well-being, but the researchers did adjust their figures to take account of factors known to affect mental health, such as an area鈥檚 income level and employment rate.
Another critique of the study is that factors that weren鈥檛 adjusted for could be worsening everyone鈥檚 mental health within a class, such as having a bully present or a poor teacher. But that is less likely because the effects were seen for several years after the children turned 16, says at the University of Oxford, who wasn鈥檛 involved in the study. 鈥淚t is unlikely to be explained by the class going through a difficult experience.鈥�
If transmission is real, it could be happening in several ways. For instance, a known phenomenon in psychology is 鈥渃o-rumination鈥�, where two friends who have depression or anxiety tend to talk excessively about negative experiences, leading to both their moods spiralling downwards.
There may also be unconscious effects at work. Teens who hear about mental health problems through their friends may be more likely to interpret everyday stress or distress in a medical light.
Some young people might also be envious of affected classmates for getting more attention or support, then exaggerate any similar symptoms themselves.
On the other hand, people being more likely to seek support because of a friend鈥檚 diagnosis could also be helpful by getting them earlier treatment, says team member 聽also at the University of Helsinki. 鈥淭his kind of normalisation of treatment and diagnosis could be considered a beneficial transmission of mental disorders.鈥�
If mental health conditions really are socially contagious, it suggests several possible routes for prevention. For instance, if one person in a class develops an eating disorder, adults may want to be more alert to any similar signs in their classmates. Alternatively, when classes are allocated, schools may consider putting someone who is thought to be at risk in with teens who seem more resilient, says Andrews.
It also suggests that education campaigns about mental health should explain the difference between everyday distress and a clinical condition. 鈥淲e have to be careful that we don鈥檛 overtreat and think that normal reactions are somehow abnormal behaviour,鈥� says Hakulinen.
Andrews, along with his colleague , also at the University of Oxford, previously proposed the 鈥減revalence inflation hypothesis鈥� about mental health conditions, which says that rates are rising partly because well-intended awareness campaigns contribute to this kind of medicalisation of life鈥檚 normal ups and downs.
The idea that mental ill health can spread through groups of teens may make some people feel uncomfortable, and the latest study is by no means clinching proof that this is happening, says Andrews. Yet the findings are another piece of the puzzle that might let us understand the complex mechanisms behind the youth mental health epidemic 鈥� and anything that helps us combat such an important public health problem seems worth paying attention to.
Jama Psychiatry
