Repeated bullying can affect 49 brain regions

The transition from childhood to adulthood during adolescence is a complex process. Bullying — manifesting as social exclusion, verbal abuse, and physical violence —adds another layer of stress for young people at this stage. The largest pan-European study to date, involving 2,049 victims, reveals that bullying — which affects one in three students worldwide — also impacts brain development. The study, published in the journal bioRxiv, indicates that at least 49 brain regions responsible for memory, learning, and motor control may be affected.

Michael Connaughton, a researcher at Trinity College, and colleagues from the PRADO research group analyzed responses to a five-item questionnaire and MRI scans of adolescents aged 14, 19, and 22 from Germany, Ireland, the U.K., and France. While previous studies have established that bullying leads to detrimental mental health consequences that often persist into adulthood, this research suggests that bullying may influence overall brain development. The study also identified differences in how boys and girls respond to bullying.

The co-author of the study, Darren Brody, from the Department of Psychiatry at the Royal College of Surgeons in Ireland, posits that these differences may stem from the types of aggression typically experienced by each gender. MRI images showed greater activation in specific areas of the brain for girls, including the left nucleus accumbens, linked to psychological reward systems and motivation, and the right amygdala, which plays a role in managing the nervous system.

“Girls are generally more likely to experience emotional manipulation, such as ostracism by their peers,” he explains. Conversely, boys exhibited responses related to physical coordination in motor and sensory regions like the right precentral gyrus, likely reflecting their experiences of physical bullying. Brody notes: “In boys’ brain responses, it was not as obvious that emotional centers were enlarging.”

During adolescence, the brain is in a phase of development that makes it especially vulnerable to stressors. Much like a gardener pruning weeds in a park, this stage involves synaptic pruning or readjustment of neurons and their connections, which leads to profound neurophysiological changes. Alessandro Massaro, a PhD in Clinical and Health Psychology, says that during this period, adolescents exhibit heightened sensitivity to both negative emotions (fear, anxiety, or shame) and positive emotions (joy, love, and happiness).

“There is a shift in reference figures from parents to peers, and when young people struggle to belong to a group, this situation can be extremely difficult for them to cope with,” explains Massaro, who was not involved in the study. The findings indicate that bullying victimization is associated with a decrease in total gray matter volume in both sexes, suggesting a widespread impact on brain development in response to chronic stress. Concurrently, the stress response leads to hyperactivation of the limbic system, which mediates emotions and memory. According to the authors, this hyperactivation may result in an increased response volume in these regions as the brain attempts to regain control.

Experts acknowledge that while causality cannot be definitively proven — meaning it remains unclear whether the observed brain changes are due to inherent characteristics of bullying victims — they argue that in the three age groups analyzed, bullying was consistently linked to alterations in brain growth curves. Professor Ignacio Morgado from the Institute of Neuroscience at the Autonomous University of Barcelona concurs, noting that although the sample size is substantial, the conclusions are preliminary and will aid further investigation into the long-term consequences of bullying.

“As it is a correlational study, we cannot say 100% that it is the cause of these changes in the brain. The loss of neurons is already well documented in cases of stress,” says Morgado, who was not part of the research. In 2018, researchers at King’s College London discovered physical structural differences in the brains of adolescents who are regularly bullied, though the study involved only 682 participants. Additionally, a more recent analysis from the University of Tokyo, published in February 2024, revealed that the brains of bullying victims exhibit chemical changes linked to psychosis.

“Not all cases are the same, and we would like to study in depth the more subtle forms of harassment, such as those experienced by women,” adds Brody.

Bullying is a social phenomenon

Bullying emerges and develops within a complex network of interpersonal relationships, often leaving teenagers feeling compelled to remain silent about their experiences. Rosario Ortega, a professor of Developmental and Educational Psychology at the University of Córdoba in Spain, emphasizes that bullying is not a pathological phenomenon. “Cruelty is not a disease; it is an immoral behavior that can cause significant harm to someone. The victim needs support when they are affected,” she explains.

To effectively tackle this issue, Ortega stresses the importance of open communication between parents and guardians of teenagers. Javier Miglino, director of the NGO Bullying Without Borders and a proponent of World Day Against School Bullying, believes that addressing bullying requires a diligent, grassroots approach implemented in schools one at a time. “It’s a good idea to investigate the root causes to stop it from occurring,” he adds.

Experts agree that early interventions can help mitigate the devastating psychological consequences of bullying in young people. Cognitive-behavioral therapy, in particular, can empower victims who have endured repeated attacks to “adopt a more resilient mindset,” as highlighted in the study.

Additionally, fostering transparency in how schools address bullying can enhance the overall climate of coexistence. “When someone is abusive, it is important for the school administration to intervene to ensure that no victims are overlooked,” says Ortega.

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