The brains of teenagers with serious antisocial behaviour problems differ significantly in structure to those of their peers, according to a new study which found that the actions of unruly teens may stem from changes in brain development in early life. Researchers from University of Cambridge and University of Southampton in the UK used magnetic resonance imaging (MRI) methods to look at the brain structure of male adolescents and young adults who had been diagnosed with conduct disorder. This included persistent behavioural problems including aggressive and destructive behaviour, lying and stealing, and for older children, weapon use or staying out all night. In particular, researchers looked at the coordinated development of different brain regions by studying whether they were similar or different in terms of thickness. Regions that develop at similar rates would be expected to show similar patterns of cortical thickness, for example. "There is evidence already of differences in the brains of individuals with serious behavioural problems, but this is often simplistic and only focused on regions such as the amygdala, which we know is important for emotional behaviour," said Luca Passamonti from University of Cambridge. "But conduct disorder is a complex behavioural disorder, so likewise we would expect the changes to be more complex in nature and to potentially involve other brain regions," said Passamonti. Researchers recruited 58 male adolescents and young adults with conduct disorder and 25 typically-developing controls, all aged between 16 and 21 years. They divided the individuals with conduct disorder according to whether they displayed childhood-onset conduct disorder or adolescent-onset conduct disorder. Researchers found that youths with childhood-onset conduct disorder (sometimes termed 'early-starters') showed a strikingly higher number of significant correlations in thickness between regions relative to the controls. They believe this may reflect disruptions in the normal pattern of brain development in childhood or adolescence. Youths with adolescent-onset conduct disorder ('late starters') displayed fewer such correlations than the healthy individuals. Researchers believe this may reflect specific disruptions in the development of the brain during adolescence, for example to the 'pruning' of nerve cells or the connections (synapses) between them. "The differences that we see between healthy teenagers and those with both forms of conduct disorders show that most of the brain is involved, but particularly the frontal and temporal regions of the brain," said Graeme Fairchild from University of Southampton. "This provides extremely compelling evidence that conduct disorder is a real psychiatric disorder and not, as some experts maintain, just an exaggerated form of teenage rebellion," said Fairchild. The findings were published in the Journal of Child Psychology and Psychiatry.