Why do some adolescents leap from thought to action when it comes to self-harm? In other words, why do they self-harm? The answer may lie in the skin. A new British study shows that children with a history of self-harm exhibit abnormal electrodermal reactions even to neutral stimuli.
It's a biological signal that clearly distinguishes them from those who merely think about it. The difference is measurable and could change the way we identify those who are truly at risk.
The skin that doesn't lie
The team led by Karen Wetherall e Rory O'Connor ofUniversity of Glasgow has published on Nature Mental Health a study that identifies for the first time a specific biological marker linked to self-harm behavior in youth.
The researchers measured the electrodermal activity (EDA) of 180 young people between the ages of 16 and 25, divided into three groups: those who had never thought about harming themselves, those who had thought about it but never acted, and those who had actually committed acts of self-harm in the last year.
Electrodermal activity measures the skin's ability to conduct electricity. When we're calm, the skin's electrical resistance is high. When we experience stress, fear, or excitement, this resistance drops sharply due to the activation of the sweat glands and the sympathetic nervous system. It's a bit like an emotion detector hidden beneath the surface.
Young people who had injured themselves showed an electrodermal response significantly higher Compared to the other two groups, both during stressful tasks and when faced with neutral stimuli like simple beeps, their bodies reacted as if constantly on high alert, even when there was nothing threatening.
Self-harm: How and why kids hurt themselves
The ways in which adolescents inflict injuries on themselves are many and often hidden. cutting of the skin (especially on the arms, thighs and abdomen) with razor blades, razors or scissors is the most common practice. Followed by to scratch to the point of creating wounds, the to burn with cigarettes or flames, the to hit each other violently against hard surfaces, biting and pulling out hair. Gestures that leave visible marks, but which Boys learn to hide creative excuses under long sleeves, oversized sweatshirts.
The most common reason? Managing overwhelming emotions. As Professor O'Connor explains:
For many young people, self-harm is a dysfunctional way to relieve tension, anger, anxiety, or depression. Physical pain paradoxically becomes more manageable than emotional pain.
Scientific literature indicates that among the 15% and 20% of Italian adolescents have engaged in self-harm at least once, with a typical onset between the ages of 13 and 14. Girls are more involved, in a ratio of approximately 2:1 compared to boys.
The laboratory and the three experiments
The researchers presented the participants with three different tasks. In the first, they repeatedly played neutral tones to measure the rate of habituation (how quickly the body stops reacting to a repeated stimulus). In the second, induced psychosocial stress through time-pressured cognitive tasks. In the third, they showed images with emotional content.
The results were clear. Those who had a history of self-harm showed aelectrodermal hyperreactivityTheir bodies adjusted more slowly to the repeated tones and overreacted to stressful stimuli. It was as if their emotional alert system were set to a sensitivity that was too high, impossible to modulate.
Self-harm: From Biomarkers to Prevention
The discovery has concrete implications. Currently, identifying those truly at risk relies primarily on questionnaires and clinical interviews. An objective biomarker could change things. “Distinguishing what makes a young person vulnerable to the transition from thought to action is crucial,” explains Dr. Wetherall.
"Previous findings on self-harm were unclear. Now we have a more precise picture."
Professor O'Connor adds that "our findings suggest that the way young people process emotions may be key. Interventions targeting emotion regulation strategies could be particularly effective." Techniques such as electrodermal biofeedback (already used for eating disorders and anxiety) could be adapted to help children recognize, monitor, and control their dysregulated physiological responses.
It's worth remembering that self-harm is not just an individual cry for help, but also a structural problem.
As documented in recent cases, social media has amplified exposure to content that normalizes these practices, creating real digital epidemics of self-harming behaviorsSelf-harm is not an “acceptable” or “understandable” state of being, nor a “free expression of the self”: it is the sign of a malaise that requires affection, attention, respect, and presence.
Science needs to act quickly
The study has limitations. The sample size was not as large as expected due to COVID-19, and the number of males in the group with a history of self-harm was lower than expected. Furthermore, other physiological indicators of stress, such as heart rate or cortisol, were not measured. Yet, the contribution to combating self-harm is significant.
The skin, after all, is the front line: the boundary between us and the world. When a teenager injures it, he's trying to shift that boundary, to control something he feels is slipping away. Now we know that that border reacts differently, that there is a biological signature behind the discomfort. It remains to be seen whether we will be quick enough to use this knowledge to help those who, silently, are already deciding whether to harm themselves or not.
