Toddlers' aggression linked to genetic factors

A new study has found that the development of physical aggression in toddlers is strongly associated genetic factors and to a lesser degree with the environment.

Eric Lacourse of the University of Montreal worked with the parents of identical and non-identical twins to evaluate and compare their behavior, environment and genetics.

"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 behavior," the researcher said.

Lacourse and his colleagues posited and tested three general patterns regarding the developmental roles of genetic and environmental factors in physical aggression.

First, the most consensual and general point of view is that both sources of influence are ubiquitous and involved in the stability of physical aggression. Second, a "genetic set point" model suggested a single set of genetic factors could account for the level of physical aggression across time.

A third pattern labeled 'genetic maturation' postulates new sources of genetic and environmental influences with age.

The researcher said that according to the genetic maturation hypothesis, new environmental contributions to physical aggression could be of short duration in contrast to genetic factors.

The study is published in journal Psychological Medicine.