Mothers counteract genetic aggression risk

Good mothering can cancel out a genetic predisposition to aggressive behaviour in monkeys, a new US study suggests. Scientists at the National Institutes of Health say that a nurturing environment can curb antisocial behaviour in rhesus monkeys born with low levels of certain brain chemicals. Their findings, which will be published in later this year in the journal Biological Psychiatry, mirror earlier research on another genetic alteration linked to aggression in humans.

Stephen Suomi and colleagues studied a large population of rhesus monkeys, around 5-10 per cent of which showed excessive levels of violent, antisocial behaviour. They found that these aggressive monkeys had a 'short' version of a gene called 5HTT, which is linked to low levels of the 'feel-good' brain chemical serotonin - 5HT(5-hydroxy-tryptamine).

In another study, the researchers looked at the effects of nurturing on the monkeys prone to aggressive behaviour, by comparing animals raised by their mothers with those left with their siblings to fend for themselves. They found that monkeys with low serotonin levels became extremely aggressive when abandoned, but behaved normally if reared in a supportive, nurturing way by their mothers. 'It's a gene-environment interaction. There's a buffering effect of good mothering', said Suomi. However, he stressed that the findings were in animals, and could not be generalised to humans, saying there could be 'many, many more' genes involved.

A 2002 study, carried out by researchers at King's College in London, found that children were more likely to be aggressive if they inherited a particular version of a gene called MAOA (monoamine oxidase A). The MAOA gene makes a protein called monoamine oxidase A, which helps control levels of brain chemicals such as serotonin. However, as in the latest study, a genetic predisposition to antisocial behaviour appeared to be heavily influenced by upbringing: children who inherited the MAOA variant behaved normally if they were mothered well.

Researchers are gathering at a meeting this week in London, to discuss the implications of the latest work on genetics and behaviour. 'One question we're looking at is opportunities for pharmacogenomics', said US expert Donald Pfaff. 'The use of cleverly designed drugs to control inappropriate aggression and violence [could] bring that individual into a range where normal social controls, including a good family environment and good school environments, can work', he told a press conference.