...researchers are beginning to unravel how specific genes and the social environment interact to produce changes in the brain that influence emotional control and violence in kids. One of the most exciting advances came in 2002, when Moffitt's group focused on the gene for the enzyme monoamine oxidase A. Variants of MAO-A 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 team looked at the interaction between MAO-A, criminality and abuse as a child - a known risk factor for future antisocial behaviour (Science, vol 297, p 851).
The whole article is well worth reading. The variant of MAO-A is crucial, apparently, in the sense that kids who have a low-enzyme activity variant of this are far more likely to be badly damaged by abuse and neglect. This is one of those key questions: why do some kids flourish despite terrible upbringings, and why are others so crushed?
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. 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.
10 times more likely. That is enormous.
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