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Brain change link to yob behaviour

Teenage yob behaviour can be traced to physical changes in the growing brain that may be linked to poor parenting, say scientists.

A new British study shows for the first time that emotional centres of the brain are strikingly stunted in boys with conduct disorder (CD), even when the problems first appear in adolescence.

Conduct disorder is a recognised psychiatric condition characterised by aggressive and antisocial traits, and rates have increased sharply around the world since the 1950s.

It affects about 5% of school-age children and involves classic "yob" behaviour such as acts of violence, fighting, weapon use, pathological lying, thieving and breaking into homes.

The condition can develop in young children, or not show itself until the teenage years. Those affected are at greater risk of mental problems, substance abuse and criminality in later life.

It has long been thought that adolescent-onset CD is merely the result of susceptible teenagers imitating badly behaved peers but the new research, funded by the Wellcome Trust and Medical Research Council, challenges this view, pointing to brain changes that affect all youngsters with the condition.

The highlighted brain areas are the amygdala and insula, which contribute to emotional perception, empathy, and the ability to recognise when others are in distress.

Magnetic resonance imaging brain scans showed both regions were significantly smaller in affected teenagers, including those who only became badly behaved when they reached adolescence. Sophisticated computer processing was used to identify the differences, and revealed that insula volume reduced with the severity of behavioural problems.

The scientists are cautious about how to interpret the findings, published in the American Journal of Psychiatry online. But they point out there is already evidence of links between conduct disorder and home environment.

Co-researcher Dr Graeme Fairchild, from the University of Southampton, said: "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."

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