Factors such as household income, parents' education, and antisocial behavior during adolescence may play a role in determining whether children exhibit a high level of physical aggression, new research suggests.

The study provides new insight into why some boys whose mother might not perceive them as physically aggressive before starting school display such behavior later on, as rated by teachers and self-reports. To help identify children at risk for aggressive behavior, the authors suggest that healthcare professionals carry out assessments during well-child visits and that preventive interventions be tested with at-risk families during pregnancy and early childhood.

"Family doctors and obstetricians are the first lines, followed by pediatricians," author Richard E. Tremblay, Ph.D., professor emeritus, Departments of Pediatrics and Psychology, University of Montreal, Canada, told Medscape Medical New. "Psychiatrists and obstetricians should collaborate during pregnancy." The study was published online December 28 in JAMA Network Open.

Research shows that children start to be physically aggressive during their first two years of life and that aggression peaks in frequency between ages 2 and four years. Tremblay and his research group were the first to report that physical aggression peaks that early in childhood. In 2017, he won the Stockholm Prize in Criminology.

The jury that awarded the prize cited, among other things, his work showing that the peak age for violent behavior is not age 20 but age 3 and noted that this has many implications for violence prevention and intervention policies. In most cases, this high frequency of physical aggression in early childhood declines before children enter school and then continues to decrease. However, for a small proportion of children, the frequency of physical aggression remains high during middle childhood and adolescence.

Negative Outcomes

This behavior is associated with a range of adverse outcomes in adolescence and adulthood, such as increased risk of violent crime, school failure, alcohol and drug abuse, and social maladjustment. The new study used data from the Quebec Longitudinal Study of Child Development (QLSCD), a cohort study of a representative, population-based sample of 2223 infants born in 1997 and 1998 in the Canadian province of Quebec.

Trained research assistants conducted interviews with parents, mostly mothers, starting when the child was five months old. Subsequent meetings with the parent took place when the children were aged 1.5, 2.5, 3.5, 4.5, 5, 6, and eight years.