Can’t figure out why your toddler is throwing toys at you or hitting his/her sibling?

Blame it on genes.

The development of physical aggression in toddlers is strongly associated with genetic factors and to a lesser degree with the environment, says a study.

“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,” said Eric Lacourse of University of Montreal and its affiliated CHU Sainte-Justine Hospital in Canada.

The team worked with parents of identical and non-identical twins to evaluate and compare their behaviour, environment and genetics.

However, 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, noted the study published in the journal Psychological Medicine.

The study on early childhood physical aggression indicates that physical aggression starts during infancy and peaks between the ages of 2 and 4.

It also shows that there are substantial differences in both frequency at onset and rate of change of physical aggression due to the interplay of genetic and environmental factors over time.

Long-term studies of physical aggression clearly show that most children, adolescent and adults eventually learn to use alternatives to physical aggression.

“Because early childhood tendencies may evoke negative responses from parents and peers, early physical aggression needs to be dealt with care,” cautioned Lacourse.

“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,” he said.

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