Page "Monoamine oxidase" Paragraph 22

A study based on the Dunedin cohort concluded that maltreated children with a low-activity polymorphism in the promoter region of the MAO-A gene were more likely to develop antisocial conduct disorders than maltreated children with the high-activity variant.

Out of the 442 total males in the study ( maltreated or not ), 37 % had the low activity variant.

Of the 13 maltreated males with low MAO-A activity, 11 had been assessed as exhibiting adolescent conduct disorder and 4 were convicted for violent offenses.

The suggested mechanism for this effect is the decreased ability of those with low MAO-A activity to quickly degrade norepinephrine, the synaptic neurotransmitter involved in sympathetic arousal and rage.

This is alleged to provide direct support for the idea that genetic susceptibility to disease is not determined at birth, but varies with exposure to environmental influences.

However, most individuals with conduct disorder or convictions did not have low activity of MAO-A ; maltreatment was found to have caused stronger predisposition for antisocial behavior than differences in MAO-A activity.