The study, funded jointly by the Wellcome Trust and the Medical Research Council, reveals that the brain differences were present regardless of the age of onset of the disorder, challenging the view that adolescence-onset conduct disorder (CD) is merely a consequence of imitating badly behaved peers.
CD is a psychiatric condition characterised by increased aggressive and antisocial behaviour. It can develop in childhood or in adolescence and affects around five out of every 100 teenagers in the UK. Those affected are at greater risk of developing further mental and physical health problems in adulthood.
Neuroscientists at the University of Cambridge and the MRC Cognition and Brain Sciences Unit used magnetic resonance imaging to measure the size of particular regions in the brains of 65 teenage boys with CD compared with 27 teenage boys who did not display symptoms of behavioural disorder.
Their findings revealed that the amygdala and insula - regions of the brain that contribute to emotion perception, empathy and recognising when other people are in distress - were strikingly smaller in teenagers with antisocial behaviour. The changes were present in childhood-onset CD and in adolescence-onset CD, and the greater the severity of the behaviour problems, the greater the reduction in the volume of the insula.
Smaller volume of structures in the brain involved in emotional behaviour has been linked to childhood-onset CD, in which behavioural problems manifest early in life. However, adolescence-onset CD was previously thought to be caused solely by the imitation of badly behaved peers. The current findings cast doubt on this view and suggest a potential neurological basis for these serious and challenging conditions, whether they emerge in childhood or adolescence.
Ian Goodyer, Professor of Child and Adolescent Psychiatry at the University of Cambridge, and Dr Graeme Fairchild, now based at the University of Southampton, led the research. Dr Fairchild explained: "Changes in grey matter volume in these areas of the brain could explain why teenagers with conduct disorder have difficulties in recognising emotions in others. Further studies are now needed to investigate whether these changes in brain structure are a cause or a consequence of the disorder."
Professor Goodyer added: "We hope that our results will contribute to existing psychosocial strategies for detecting children at high risk for developing antisocial behaviour."
Dr Andy Calder from the MRC Cognition and Brain Sciences Unit, who co-led the research, commented: "Studies such as this are tremendously important in understanding the causes of conduct disorder. Only when we are confident that we understand why the disorder develops can we apply this knowledge to the further development and evaluation of treatments. The disorder has a devastating impact on families and communities, and at the moment, we have few effective treatments."
The group have previously shown that individuals with both forms of conduct disorder display abnormal patterns of brain activity, but this new work marks an important advance in understanding the biology of aggression and violence by showing that differences in brain structure are linked to the disorder.
The study will appear online today in the 'American Journal of Psychiatry'.
Fairchild G et al. Brain structure abnormalities in early-onset and adolescent-onset conduct disorder. Am J Psych [epub ahead of print].
About the Medical Research Council
For almost 100 years the Medical Research Council has improved the health of people in the UK and around the world by supporting the highest quality science. The MRC invests in world-class scientists. It has produced 29 Nobel Prize winners and sustains a flourishing environment for internationally recognised research. The MRC focuses on making an impact and provides the financial muscle and scientific expertise behind medical breakthroughs, including one of the first antibiotics penicillin, the structure of DNA and the lethal link between smoking and cancer. Today MRC funded scientists tackle research into the major health challenges of the 21st century.
About the University of Cambridge
The University of Cambridge’s mission is to contribute to society through the pursuit of education, learning and research at the highest international levels of excellence. It admits the very best and brightest students, regardless of background, and offers one of the UK's most generous bursary schemes.
The University of Cambridge's reputation for excellence is known internationally and reflects the scholastic achievements of its academics and students, as well as the world-class original research carried out by its staff. Some of the most significant scientific breakthroughs occurred at the University, including the splitting of the atom, invention of the jet engine and the discoveries of stem cells, plate tectonics, pulsars and the structure of DNA. From Isaac Newton to Stephen Hawking, the University has nurtured some of history's greatest minds and has produced more Nobel Prize winners than any other UK institution with over 80 laureates.
About the University of Southampton
The University of Southampton is a leading UK teaching and research institution with a global reputation for leading-edge research and scholarship across a wide range of subjects in engineering, science, social sciences, health and humanities. With over 22,000 students, around 5,000 staff, and an annual turnover well in excess of £400 million, the University of Southampton is acknowledged as one of the country's top institutions for engineering, computer science and medicine. We combine academic excellence with an innovative and entrepreneurial approach to research, supporting a culture that engages and challenges students and staff in their pursuit of learning.
The University is also home to a number of world-leading research centres including the Institute of Sound and Vibration Research, the Optoelectronics Research Centre, the Web Science Research Initiative, the Centre for the Developmental Origins of Health and Disease, the Southampton Statistical Sciences Research Institute and is a partner of the National Oceanography Centre at the Southampton waterfront campus.
About the Wellcome Trust
The Wellcome Trust is a global charitable foundation dedicated to achieving extraordinary improvements in human and animal health. It supports the brightest minds in biomedical research and the medical humanities. The Trust's breadth of support includes public engagement, education and the application of research to improve health. It is independent of both political and commercial interests.