Identifying Children at Risk for Physical Aggression

Pauline Anderson

January 04, 2019

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.

Dr Richard Tremblay

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 line, followed by pediatricians," author Richard E. Tremblay, PhD, professor emeritus, Departments of Pediatrics and Psychology, University of Montreal, Canada, told Medscape Medical News. "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 2 years of life and that aggression peaks in frequency between ages 2 and 4 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 negative outcomes in adolescence and adulthood, such as increased risk for 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 5 months old. Subsequent interviews with the parent took place when the children were aged 1.5, 2.5, 3.5, 4.5, 5, 6, and 8 years.

During the earliest interview with mothers, researchers obtained information on various family risk factors.

Teachers assessed the child's behavior at ages 6, 7, 8, 10, 12, and 13 years. The children provided self-reports of behavior problems when they were 10, 12, and 13 years old.

The mean response rate for mothers' ratings was 80.9%. For teachers, the mean response rate was 45.7%, and the mean response rate for self-ratings was 57.9%.

Biting and Kicking

Physical aggression was defined as "gets into fights," "physically attacks others," and "hits, bites, kicks other children." Respondents rated these on a 3-point Likert-type scale as never (1 point), sometimes (2 point), or often (3 points).

Researchers used multitrajectory modeling that approximates an underlying, unknown continuous distribution of developmental patterns. The authors stress that the trajectories are not fixed and should only be regarded as explanatory models for possible developmental outcomes.

The study required that participants undergo at least 10 of the 16 observations.

Among 2223 participants, 51.2% were boys, and 91.2% were of white race/ethnicity.

As expected, the study found significant sex differences across all assessment times, with girls having lower levels of physical aggression and lower variance, especially as reflected in teacher ratings.

According to all ratings, the frequency of physical aggression in boys and girls increased from age 1.5 years to age 3.5 years, when frequency was at the highest, and then substantially decreased until age 13 years.

Distinct Trajectories

The researchers uncovered three distinct developmental trajectories of physical aggression for girls and five for boys.

Girls on the high trajectory (group 3) were significantly different from those on the low trajectory (group 1) with respect to the family risk factors measured 5 months after the child's birth. These factors included the mother's and father's education, household income, maternal and paternal depression, socioeconomic status, the number of siblings at birth and at 17 months, and the father's antisocial behavior during his own adolescence.

"This group of girls is clearly at high risk of numerous problems during adolescence and adulthood, including having children who will have similar problems," commented Tremblay. "They are clearly the ones who need support early on to prevent the next generation of behavior problems."

Girls on a trajectory of high physical aggression during early childhood (according to mothers) remain on the high physical aggression trajectory from ages 6 to 13 years, as demonstrated in teacher ratings and self-reports.

This finding, said Tremblay, suggests that "we can rely on mother reports for girls early on." This was not so much the case with boys, though.

The 6.0% of boys who were on the high physical aggression trajectory (group 5) according to teacher ratings and self-ratings were not on the highest physical aggression trajectory from ages 1.5 to 8 years according to ratings by mothers.

For this group of boys, the family risk factors that were assessed 5 months after the child's birth indicated that these boys were living in family conditions of very high risk.

"This is the first time that we showed this discrepancy between mother ratings, teacher ratings, and self-reports," commented Tremblay.

"We suggest that these mothers have more difficulty understanding the aggression problems of their boys than of their girls. They appear to think that their son's behavior is normal. It may also be true that their aggression increases as they enter school."

Objective Sources

Researchers need information from a more objective source than the mother during early childhood, said Tremblay. "But this is very difficult if they don't go to child care and there is no father or the father does not do the assessments," which was true for the majority of fathers of families included in the study.

Although the reliability of some parent reports may be questionable, those from teachers are very reliable, said Tremblay. "The teachers are different every year, but reports are very similar among teachers and are very similar to those of the children."

These new results reinforce the idea that family characteristics of those who have long-term aggression problems can be identified during pregnancy and early childhood, said Tremblay. "That's the best time to start giving support."

For example, he said, obstetricians can identify at-risk families at the start of pregnancy and refer these families for home visitation from pregnancy to school entry. And at day care, support can be given to day care staff and to the children and parents, said Tremblay.

"Our study should also change practices in schools where resources are concentrated in late elementary school rather than kindergarten because, as the boys become bigger, they cause more damage. We need to help aggressive children when they're small."

Tremblay and his colleagues are launching a large randomized controlled trial targeting at-risk children and their families as these children enter day care. "Support will be provided to families, but also to the day care staff," he said.

A limitation of the current study was that the sample consisted primarily of children of white race/ethnicity. Also, the dropout rate was high and was more so among families of lower socioeconomic status, those with a single parent, and those in which the mother was young.

However, the results showed that attrition took place equally in all trajectory groups. This, say the authors, provided some evidence that the findings were not altered by attrition.

Barriers to Intervention

Asked to comment, Scott Benson, MD, a child and adolescent psychiatrist in private practice in Pensacola, Florida, said the study was interesting but reinforced what clinicians already know.

"I think we always knew that where you have certain risk factors, those are the children who are more likely to be violent," he said.

He agreed that early interventions, such as having counselors and other support systems in schools, would be beneficial, but "there are so many barriers to getting those early interventions."

Such barriers, he said, include a shortage of child and adolescent psychiatrists and other therapists, as well as a health insurance industry that is not that keen on funding treatments.

Benson also noted the high attrition rate among families in the study. "The problem is that you can't do long-term studies if the people aren't staying around long term."

Even if experts identified children at high risk of committing violence and those children received some form of long-term treatment, "they're not likely to stay in treatment," said Benson.

Research suggests that intervening with parents may prove more successful.

"You have to teach parents how to do better, more consistent, reliable parenting," said Benson. For example, he said, research suggests that "if your family has dinner together, it's less likely that you will end up in juvenile court."

Sitting down to dinner, with telephones and televisions turned off, and having the family engage in conversation becomes a pleasant "social event," he said. "This is a fabulous, simple intervention, but families don't do that."

The study was supported by the Canadian Institutes of Health Research, Social Sciences and Humanities Research Council of Canada, the Quebec Health Research Fund, and the Quebec Social Science and Culture Research Fund. The authors and Dr Benson have disclosed no relevant financial relationships.

JAMA Netw Open. Published online December 28, 2018. Full text

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