Good mothering can abolish the impact of a 鈥渂ad鈥� gene for aggression, suggests a new study, adding spice to the 鈥渘ature-versus-nurture鈥� controversy.
The findings come at a time when governments in Britain and Australia are seeking ways to crack down on antisocial behaviour, and refocus attention on the impacts of parenting.
The new work, on rhesus monkeys, backs an earlier study in people which gave the same result. 鈥淲e think the findings are striking in parallel with the human studies,鈥� says Stephen Suomi of the US National Institute of Child Health and Human Development in Bethesda, Maryland.
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Speaking on Monday at a press conference in London to mark the opening of a conference on genes and aggression, Suomi said that his results strongly mirror those of a study in 2002 co-led by Terrie Moffitt of the Institute of Psychiatry at King鈥檚 College London (Science, vol 297, p851).
For 26 years, she and her colleagues followed the fate of 1037 children born in 1972 in Dunedin, New Zealand. They found that children were much more likely to grow up to be aggressive and antisocial if they had inherited a 鈥渟hort鈥� version of a gene called MAOA. It makes monoamine oxidase A, an enzyme which helps to break down neurotransmitters such as serotonin, and was less efficient in the individuals with the 鈥渟hort鈥� version.
But carriers only went off the rails if they had had an awful, abusive upbringing. Carriers with good mothering were usually completely normal, showed the New Zealand study. Now, Suomi has replicated the finding in the monkeys, showing that carriers of the 鈥渟hort鈥� MAOA gene only turned bad when denied good mothering. 鈥淕ood mothering has a buffering effect,鈥� he says.
Sheer survival
Suomi was reluctant to say what his findings might mean in humans. 鈥淢aking cross-species analyses is always a dangerous thing,鈥� he says. But an obvious implication is that a 鈥渂ad鈥� gene in humans could potentially be kept in check by good parenting.
鈥淭he general principle of parenting is important and can have impacts not only at the level of behaviour, but also in hormonal activities, brain chemistry, structure and function, and at the level of gene expression,鈥� he says.
Failure to provide the correct mothering may reset the brain鈥檚 circuitry irreversibly to patterns of antisocial behaviour, aggression and self-destruction, possibly to enable sheer survival in the absence of motherly protection during infanthood.
Although the complex genetics and biochemistry have yet to be worked out, the research could ultimately lead to drugs which compensate for the 鈥渂ad鈥� genes, or prenatal screening tests which ensure that infants at risk receive optimal mothering in their first two years of life.
Suomi鈥檚 latest results have been accepted for publication in Biological Psychiatry.
