Genetic Factors Explain Substantial Part of Physical Aggression Differences

Eric Lacourse, Ph.D.  Professeur agrégé  Département de sociologie  Université de Montréal  Groupe de Recherche sur l'Inadaptation Psychosociale chez l'enfant (GRIP)  Centre de Recherche de l'Hôpîtal Interview with:
Eric Lacourse, Ph.D. 
Professeur agrégé
Département de sociologie
Université de Montréal
Groupe de Recherche sur l’Inadaptation Psychosociale chez l’enfant  Centre de Recherche de l’Hôpîtal Ste-Justine What are the main findings of the study?

Dr. Lacourse: The gene-environment analyses revealed that early genetic factors were pervasive in accounting for developmental trends, explaining most of the stability and change in physical aggression, ” Lacourse said. “However, it should be emphasized that these genetic associations do not imply that the early trajectories of physical aggression are set and unchangeable. Genetic factors can always interact with other factors from the environment in the causal chain explaining any behaviour.” Were any of the findings unexpected?

Dr. Lacourse: “The results of the gene-environment analyses provided some support for the genetic set-point hypotheses, but mostly for the genetic maturation hypotheses,” Lacourse said. “Genetic factors always explained a substantial part of individual differences in physical aggression. More generally, the limited role of shared environmental factors in physical aggression clashes with the results of studies of singletons in which many family or parent level factors were found to predict developmental trajectories of physical aggression during preschool.” Our results suggest that the effect of those factors may not be as direct as was previously thought. What should clinicians and patients take away from your report?

Dr. Lacourse: Long-term studies of physical aggression clearly show that most children, adolescents and adults eventually learn to use alternatives to physical aggression. “Because early childhood propensities may evoke negative responses from parents and peers, and consequently create contexts where the use of physical aggression is maintained and reinforced, early physical aggression needs to be dealt with care,” Lacourse said. “These cycles of aggression between children and siblings or parents, as well as between children and their peers, could support the development of chronic physical aggression What recommendations do you have for future research as a result of this study?

Dr. Lacourse: Future research should focus on similar but different phenotypes such as ADHD and ODD. They should also investigate gene-environment interactions with early adversity and other stressful life events occurring to one or both twins. Studies should also investigate how gene-environment interplay at different developmental period (childhood, adolescence and emerging adulthood).


Eric Lacourse, PhD, Michel Boivin, PhD, Mara Brendgen, PhD, Amélie Petitclerc, PhD, Alain Girard, MSc, Frank Vitaro, PhD, Stéphane Paquin, PhD candidate, Isabelle Ouellet-Morin, PhD, Ginette Dionne, PhD and Richard E. Tremblay, PhD published “A longitudinal twin study of physical aggression during early childhood: Evidence for a developmentally dynamic genome” in Psychological Medicine on January 21, 2014.