Genetic Clues May Show Impact of Early Violence on Antisocial Behavior

In a new study, researchers discovered a gene involved in the regulation of emotions and behavior could influence the long-term impact of violence experienced in childhood.

In the study, 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 followed 327 young men, some of whom were exposed to violence as children, for more than 15 years.

“We know that people who are victims or witnesses of violence in childhood are more likely to have antisocial tendencies as teenagers and adults,” said Dr. Isabelle Ouellet-Morin, a researcher at the Institut universitaire en santé mentale de Montréal.

“Genetic studies have also shown that this influence may be exacerbated through differences in DNA, such as the monoamine oxidase A (MAOA) gene,” said Ouellet-Morin, a professor with the School of Criminology at Université de Montréal.

MAOA is an enzyme that breaks down neurotransmitters like 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,” Ouellet-Morin said.

Researchers collected data from participants for over 15 years. This made it possible for the scientists to evaluate the role of the MAOA gene in various types of antisocial behavior such as partner violence and symptoms associated with an antisocial personality (e.g., engaging in illegal activities, being impulsive, showing no remorse, etc.).

Investigators also wanted to know whether the gene’s influence would be different depending on the subject’s relative exposure to violence in childhood.

  • Upon analysis of the data, researchers confirmed that exposure to violence is associated with: an increase in symptoms associated with conduct disorder in adolescence and antisocial personality in adulthood;
  • a higher likelihood of exhibiting aggressive behavior with one’s partner.

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.

Investigators discovered that on average, men who are carriers of a less frequent polymorphism of the MAOA gene (approximately 30 percent of men) are at a higher risk of exhibiting these outcomes in adolescence and 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,” said Ouellet-Morin.

Source: University of Montreal/EurekAlert