What makes us aggressive?

It's a well-documented fact that children from zero to two can be spontaneously aggressive and that boys can be among the worse culprits. Even after being socialised, seven percent of boys will continue to be hyper-aggressive until the age of nine.

According to a new study, this small subgroup of aggressive children has a different makeup than non-aggressive children.

"We know that when the mother faces adverse conditions such as poverty, stress, malnutrition, family conflicts or tobacco use during pregnancy, it will directly influence the size and weight of the foetus," says Sylvana Côté, a professor at the Université de Montréal Department of Social and Preventive Medicine and the lead researcher of this study. "These conditions are also correlated to heart disease, diabetes and child obesity."

"The education practices of the parents, as well as the transmission of a genetic profile predisposing aggressive behaviour are also contributors to atypical violent development," adds Côté, who cautions the impact of the perinatal environment on DNA methylation also has an impact.

Avant-garde research conducted by Côté and colleagues from the Groupe de recherche sur l'inadaptation psychosociale chez l'enfant (GRIP) already supports this epigenetic hypothesis. A fellow GRIP researcher demonstrated that young adults who had a hyper-aggressive profile as children and teenagers have a surmethylation of the active immune system genes that regulate the nervous system.

DNA methylation is a process that aims to protect the genome from microbes. But it can be affected by eating habits, stress, tobacco use and exterior factors such as pollution and parent care. "This type of research associated to mental disease in humans is completely new and there is much to discover in this field," says Côté.

(Source: Université de Montréal: March 2009)