Low activity of MAOA again linked to violent behavior

A new study adds to findings implicating abnormal activity of monoamine oxidase A (MAOA) in violent behavior.

MAOA is an enzyme that breaks down several neurotransmitters (messenger chemicals) which affect mood and aggression. The first clues pointing to MAOA’s role in violence emerged in 1995, when a study in the Netherlands (see related article, Crime Times, 1995, Vol. 1, No. 3, Page 1) linked a mutation in a gene coding for MAOA to impulsive aggression in the male members of a remarkably violent family. More recently (see related article, Crime Times, 2002, Vol. 8, No. 4, Page 1), a study of people abused as children showed that those with low MAOA levels were extremely likely to become antisocial adults, while those with higher MAOA activity almost never grew up to be antisocial.

In the new study, Guang Guo and colleagues asked more than 2,500 men to report any serious and/or violent delinquent acts they had committed. The researchers then determined which men carried a rare low-activity variant (2R) of the MAOA gene. The researchers report, “Men with a 2R report a level of serious delinquency and violent delinquency in adolescence and young adulthood that were about twice as high as those for participants with the other variants.” Women showed a similar but weaker pattern.