(Xinhua)
Updated: 2008-04-11 11:33

LONDON -- British scientists have identified a gene that makes some children more likely to behave badly than others.

Researchers at the Institute of Psychiatry in London uncovered enzyme called MAO-A had a link with aggression, using blood samples from a study of 535 boys and 502 girls born in New Zealand in early 1970s who were signed up at birth to the Dunedin Multidisciplinary Health and Development Study run by the University of Otago in Dunedin, according to a report on the website of the New Scientist on Thursday.

The researchers, led by Terrie Moffitt, focused on the gene for a type of enzyme monoamine oxidase A called MAO-A, variants of which they found have been linked with aggression in both animals and humans.

The enzyme breaks down neurotransmitters including serotonin - a key molecule in the regulation of aggression.

The researchers looked at the interaction between MAO-A, criminality and abuse as a child - a known risk factor for future antisocial behaviour.

Moffitt's group, using blood samples taken from the Dunedin males, examined their MAO-A variants, dividing them into high and low enzyme-activity groups. Boys were also grouped according to their experience of maltreatment (abuse in particular) in childhood.

The researchers found that the variant of the MAO-A gene the boys carried did not, by itself, predict anything about future behaviour. But when boys had the low-activity variant MAO-A and had also been abused, the result was striking.

These boys were three times as likely to be diagnosed with conduct disorder in adolescence and 10 times as likely to have been convicted of a violent crime in adulthood compared with boys of the same genotype who had not been abused.

They found boys with the high-activity variant seemed all but insulated from the effects of childhood abuse - in terms of antisocial behaviour - as there was little difference between abused boys and those who had not been abused.

Moffitt concluded that genetics account for about half of the variation in antisocial behaviour.

Identifying these genes could make it possible to intervene with treatments before children get into trouble.