Antisocial Behaviour and the Adolescent Brain: Insights from the Largest Brain Study Ever Conducted
What happens in the brains of children and young people who are frequently angry, defiant, or aggressive? The largest brain imaging study ever conducted shows that these behavioural problems are associated with subtle differences in brain structure. Dr Moji Aghajani of the Institute of Education and Child Studies is one of the lead researchers behind the study. He explains why these findings are so important.
What is antisocial behaviour?
For this study, researchers analysed MRI brain scans from more than 14.000 young people across eighteen participant groups worldwide. The research builds on a 2024 study on the same topic. But what exactly do we mean when we talk about this type of behaviour?
‘Antisocial behavioural problems are common among children and young people. They can range from irritability and disobedience to aggressive or rule-breaking behaviour. When such problems are severe and persistent, a diagnosis of conduct disorder may be made', explains Aghajani.
‘However, most young people do not fit neatly into diagnostic categories. Antisocial behavioural problems are not an all-or-nothing phenomenon', the researcher continues. Instead, they occur along a spectrum. ‘That is why we wanted to investigate how differences in behaviour, from mild to severe, relate to differences in the brain.’
More than just a diagnosis
Much previous brain research has focused on young people with a formal diagnosis of conduct disorder. While important, this mainly provides insight into the most severe cases. In this new study, the researchers adopted a broader approach.
They examined antisocial behavioural problems as a gradual scale: the more problems a young person displays, the more certain brain characteristics may change.
To do so, the researchers combined data from more than 14,000 young people aged between five and twenty-one from twelve countries across four continents. The study was conducted within the ENIGMA Antisocial Behavior Consortium. This international collaboration, co-founded and led by Aghajani, brings together researchers from around the world to make brain research on antisocial behaviour more reliable and precise.
Small differences, significant implications
The researchers found that more severe behavioural problems were associated with a slightly smaller cortical surface area, a thinner cerebral cortex, and smaller volumes of deep brain structures such as the amygdala and hippocampus. These structural differences may play a role in emotional processing, memory, empathy and decision-making.
The effects that were observed were relatively small. This means that a brain scan cannot be used to predict whether an individual young person has antisocial behavioural problems. Nevertheless, the pattern is of considerable scientific importance.
‘We do not see one major abnormal brain region that explains everything', says Aghajani.
‘Instead, we observe subtle differences spread across multiple brain systems. This fits with the idea that behavioural problems are complex and are not caused by a single brain region.’
Differences between boys and girls
One notable finding is that the associations were not the same for everyone. Among boys, behavioural problems were primarily linked to a smaller cortical surface area. Among girls, some associations were more strongly related to cortical thickness. Age also played a role, with certain associations appearing stronger in younger children.
The researchers also investigated psychopathic traits, such as significantly reduced feelings of guilt or empathy, and found that these traits influenced the relationship between behavioural problems and brain structure.
According to the researchers, this highlights the fact that behavioural problems may follow different developmental pathways. ‘We need to be cautious about relying on a single overarching explanation', says Aghajani.
‘Sex, age and individual psychological characteristics all matter.’
What does this mean for support and treatment?
The findings align with a broader movement within child and adolescent psychiatry and developmental psychology: looking not only at diagnoses, but also at individual differences and variations in symptoms. This may help researchers and clinicians better understand why some children display challenging behaviour only temporarily, while others develop persistent and severe difficulties.
The study also suggests that existing theories of antisocial behavioural problems may not fully capture the complexity of the condition. At the same time, the researchers emphasise that the findings are not yet directly applicable in clinical settings. The brain differences identified are too small to be used for individual diagnoses or treatment decisions.
However, they may help researchers develop better models of how antisocial behavioural problems emerge and develop over time.
Subtle patterns, important insights
‘This study shows that behavioural problems are linked to the brain, but in a subtle and widespread way', says Aghajani. ‘Ultimately, this insight may contribute to better prevention and intervention strategies, particularly if we gain a clearer understanding of which young people are vulnerable and at what stage.’
According to Aghajani, the study also reflects a broader shift within the field. ‘We are moving away from small, isolated studies and towards global collaborations that can uncover subtle but reliable patterns in the brain, biology and behaviour.’
The study was recently published in the leading Journal of the American Academy of Child & Adolescent Psychiatry.