BENGALURU: When a child or teenager shows persistent aggression, repeated rule-breaking or serious antisocial behaviour, people tend to reach for familiar explanations such as discord at home, poor parenting, lack of role models, bad company, weak discipline, substance abuse etc.
But two recent and major international studies; one published in The Lancet Psychiatry in 2024 and a more recent one, in The Journal of the American Academy of Child & Adolescent Psychiatry (JAACAP) this month, suggest that this view is incomplete, and that biology has a meaningful role.
Conduct problems or disorder, characterised by a repetitive and pervasive pattern of aggressive and rule-breaking antisocial behaviour, are “associated with subtle, yet widespread alterations in brain structure”, states the JAACAP paper.
Researchers for The Lancet study had analysed structural MRI scans from more than 2,400 young people across 15 international cohorts, including data from India, through the Consortium on Vulnerability to Externalising Disorders and Addictions (cVEDA).
“The central finding was clear but nuanced. Youths with conduct disorder showed widespread reductions in cortical surface area across multiple regions of the brain, particularly within frontal, parietal and temporal areas that underpin social cognition, impulse control and decision-making,” said Dr Bharath Holla, associate professor of Psychiatry, National Institute of Mental Health & Neuro Sciences (Nimhans).
He along with former senior professor, Nimhans, Vivek Benegal had analysed and contributed Indian data to the global collaboration for ‘The Lancet’ paper.
“Cortical thickness in the MRI scans was found largely unchanged, pointing to alterations in brain expansion and folding during later childhood rather than early prenatal development. The study also found smaller volumes in key subcortical regions including the amygdala, hippocampus, thalamus and nucleus accumbens, structures critical for emotion processing, learning from consequences and reward sensitivity,” explained Holla.
The JAACAP study, which drew on data from more than 14,000 children and adolescents across 18 international cohorts, including cVEDA from India, found that even milder levels of conduct problems were associated with small but widespread differences in brain structure.
“These associations included reductions in cortical surface area across much of the brain, as well as additional links with cortical thickness and smaller volumes in regions such as the amygdala and hippocampus. Importantly, these patterns were not limited to clinically diagnosed cases and were not moderated by diagnostic status, suggesting that the same neuro-developmental processes extend across the full range of behavioural variation,” added the Nimhans psychiatrist.
The JAACAP study added nuance to the earlier (Lancet) findings.
“Some associations differed by sex, with stronger surface area effects observed in boys, while certain thickness associations were more evident in girls. Associations were stronger at younger ages for some regions, highlighting developmental sensitivity. Unexpectedly, some brain-behaviour relationships were stronger at lower levels of callous-unemotional traits, underscoring heterogeneity in pathways leading to conduct problems,” he explained.
“Taken together, categorical and dimensional findings converge on the same point. These are small but consistent differences in brain development. They are not diagnostic markers, but they do shift our understanding away from purely moral or social explanations,” said Holla.
“The dimensional evidence is particularly important. It shows that these neurobiological patterns are present even before behaviour becomes clinically severe. This opens a window for earlier identification and preventive intervention,” said Dr Benegal.