Genetics of Aggression - Biological Mechanisms - Molecular Genetics

Molecular Genetics

A number of molecular genetics studies have focused on manipulating candidate aggression genes in mice and other animals to induce effects that can be possibly applied to humans. Most studies have focused on polymorphisms of serotonin receptors, dopamine receptors, and neurotransmitter metabolizing enzymes. Results of these studies have led to linkage analysis to map the serotonin-related genes and impulsive aggression. In particular, the serotonin 5-HT seems to be an influence in inter-male aggression either directly or through other molecules that use the 5-HT pathway. 5-HT normally dampens aggression in animals and humans. Mice missing specific genes for 5-HT were observed to be more aggressive than normal mice and were more rapid and violent in their attacks. Other studies have been focused on neurotransmitters. Studies of a mutation in the neurotransmitter metabolizing enzyme monoamine oxidase A (MAO-A) have been shown to cause a syndrome that includes violence and impulsivity in humans. Studies of the molecular genetics pathways are leading to the production of pharmaceuticals to fix the pathway problems and hopefully show an observed change in aggressive behavior.

A rare genetic variant causing MAO-A deficiency has been associated with violent behavior in males. In 2002 a study published by researchers at King's College London found a link between a genetic variant causing low levels of MAO-A and increased levels of antisocial behavior in people who had been mistreated as children. An American group studying monkeys called MAO-A a "warrior gene" in 2004. A 2008 study found a similar result involving the variant of the MAO-A gene, as well as the genes DAT1 and DRD2. In all three cases, the variants of these genes were associated with an elevated risk of violent and delinquent behavior, but only in people who experienced certain stresses during childhood.