Antisocial behavior: Understanding influence of genes and the environment

A gene involved in the regulation of emotions and behavior could influence the long-term impact of violence experienced in childhood on antisocial behavior. This is the finding of a longitudinal study carried out by a team of researchers at the Institut universitaire en santé mentale de Montréal (CIUSSS de l'Est-de-l'Île-de-Montréal) and Université de Montréal on 327 young men who live in Quebec (Quebec Longitudinal Study of Kindergarten Children), some of whom were exposed to violence as children.

These studies found that MAOA is an enzyme that breaks down neurotransmitters called monoamines (noradrenaline, serotonin and dopamine), and a dysfunction in its action in certain areas of the brain may disrupt the regulation of emotions and behavioral inhibition. "So far, studies investigating how the MAOA gene is involved in antisocial behavior in interaction with adverse childhood experiences have been inconsistent. We did this study to try and clarify the situation," stated Ms. Ouellet-Morin.

In short, this study has also demonstrated that the MAOA gene moderates the expression of antisocial behavior in young men who are exposed to violence as children. On average, men who are carriers of a less frequent polymorphism of the MAOA gene (approximately 30% of men) are at a higher risk of exhibiting these outcomes in adolescence and in early adulthood compared to those without this polymorphism but who also have been exposed to violence as children.

These results clearly show that genes do not hold all the answers about an individual's future, at least no more so than the environment. The debate between nature and nurture is a false one. The challenge now is to better understand the mechanisms through which either vulnerability and resilience occurs in people who are exposed to adverse life experiences. Part of the answer lies in a person's constant interaction with the environment, which includes his or her genetic baggage," concluded Ms. Ouellet-Morin.