Bad behaviour linked to gene

Analysis revealed a genetic link

The chances of anti-social behaviour among boys who are maltreated as they grow up may be determined by their genetic make-up, research suggests.

Researchers from King's College in London have found that boys who have a particular version of a gene are much more likely to go off the rails if they suffer maltreatment when young.

The results provide evidence that a person's genetic make up can influence their sensitivity to environmental factors

Professor Terrie Moffitt

The discovery raises the possibility of developing drugs to combat crime, the scientists believe.

But critics are concerned that youngsters could be labelled as potential troublemakers before they have committed any crime.

They also fear that governments may turn to using drugs to fight crime, rather than tackling deep-rooted social problems.

Enzyme levels

The gene in question controls activity of an enzyme called monoamine oxidase A (MAOA).

The researchers studied a group of young men, of whom 154 had been maltreated, 33 severely.

They found that those who carried a version of the gene linked to low levels of MAOA production were much more likely to indulge in anti-social behaviour such as violent crime.

Conversely, anti-social behaviour was much less likely among the group who carried a version of the gene linked to higher MAOA levels.

Brain chemicals

MAOA breaks down brain chemicals that have been shown to be involved in several aspects of behaviour, including aggression.

Don't add to the problem by layering in a new generation of so-called violence preventing drugs

Professor Stephen Post

Researcher Professor Terrie Moffitt said: "A third of the population have a genetic makeup associated with low activity of MAOA, and at first we could not show a link between genetic make-up and violence in the study.

"However, if those individuals with the at-risk genetic make-up were also maltreated, then they were much more likely to develop antisocial behaviour."

The researchers found 12% of the 442 individuals studied were men had been maltreated, and who had the gene linked to low MAOA levels.

However, this group were responsible for 44% of violent crimes committed by the whole sample group.

Professor Moffitt said: "The results provide evidence that a person's genetic make up can influence their sensitivity to environmental factors.

"These findings may also partly explain why not all victims of maltreatment grow up to victimise others - some genes may actually promote resistance to stress and trauma."

Professor Stephen Post, an expert in bioethics at Case Western Reserve University, Cleveland, US, warned against jumping to the conclusion that the breakthrough could be used to develop new drugs to treat anti-social behaviour.

He said: "Many people will have the genetic susceptibility and yet show remarkable resiliency in the face of maltreatment, going on to live constructive lives.

"Violence in maltreated children is a major issue. Stop the maltreatment, and don't add to the problem by layering in a new generation of so-called violence preventing drugs."