Spanking Increases Aggression, Decreases Language Skills

Deborah Brauser

October 25, 2013

More evidence shows that spanking can negatively influence a child's behavior, but the new research suggests that it can also impair cognitive development.

A cohort study of nearly 2000 children showed that those who were spanked even a little at the age of 5 years by their mothers had significantly more externalizing behaviors, such as aggression and rule breaking, at the age of 9 years than those who did not experience maternal spanking. And this association remained significant after controlling for a long list of risk factors.

In addition, those who experienced high levels of paternal spanking at the age of 5 years had significantly lower scores on a test assessing receptive vocabulary at the age of 9.

"Spanking remains a typical rearing experience for American children," write Michael J. MacKenzie, PhD, from the School of Social Work at Columbia University in New York City, and colleagues.

Joan Durrant, PhD, a clinical child psychologist and professor in the Department of Family Social Sciences at the University of Manitoba in Winnipeg, Canada, told Medscape Medical News that the investigators' finding of an association between spanking and increased aggression is not new.

"What is unique is the number of controlled variables that they included. And still the relationship held. So there is some direct effect," said Dr. Durrant, who was not involved with the research.

The investigators add that the study also provides "novel information" about how paternal spanking may play a role.

The study was published online October 21 in Pediatrics.

Maternal Spanking and Aggression

The investigators evaluated data for 1933 children who participated in the Fragile Families and Child Well-Being Study. These participants were followed from birth, which occurred between 1998 and 2000, through the age of 9 years.

Parental reports of both maternal and paternal spanking practices when their children were 3 years old and 5 years old were assessed.

When the children were 3 and again when they were 9 years of age, externalizing behaviors were measured using the Child Behavior Checklist (CBCL), including its aggression, rule-breaking, and destructive subscales.

Receptive vocabulary was also measured at the age of 9 years using the Peabody Picture Vocabulary Test (PPVT) in a subgroup of 1532 of the children.

Results showed that when the children were 3 years of age, 57% of their mothers and 40% of their fathers reported having spanked their offspring. These numbers decreased slightly to 52% and 33%, respectively, when the children were 5 years old.

Maternal spanking 2 or more times per week when their child was 3 (P < .05) or 5 years of age (P < .001) and maternal spanking fewer than 2 times per week when the child was 5 years of age (P < .001) were all associated with significantly higher levels of externalizing behaviors on the CBCL when the child was 9 years of age vs children who were never spanked.

Adding in variables such as the child's sex or birth order, low birth weight, and family sociodemographics did not change the significance of any of these associations. Adding in additional variables, such as maternal mental health and cognition and earlier child behavior, did not change the significance of the associations found when any maternal spanking occurred at the age of 5 years.

Paternal Spanking and Language

There were no associations found between paternal spanking and increased CBCL scores.

However, high levels of paternal spanking when the child was 5 years of age was associated with significantly lower vocabulary scores on the PPVT at the age of 9 years compared with children who were not spanked (P < .05).

Significance remained after adding in the child characteristics, sociodemographics, and paternal mental health and cognition variables. However, the association was no longer significant after adding in earlier child externalizing behavior.

"These results provide additional evidence as to the prevalence of spanking among US families and the effects on child behavioral and cognitive development," write the investigators.

"Our analysis is distinctive in the breadth of control variables included," they note, adding that this increased their confidence that the associations found were not "simply a spurious correlation."

They write that clinicians should educate families more about spanking and negative outcomes, as well as discuss better discipline practices that might "encourage healthy child trajectories."

Not Surprising but Important

"There have now been 30 studies showing a relationship between physical punishment and development of higher levels of aggression in children. That doesn't mean that every child that has ever been spanked becomes violent, but it means that their risk is greater," said Dr. Durrant.

Dr. Joan Durrant

"There's also some evidence that physical punishment causes children stress, and stress really has an impact on the emotional centers of the brain. So the current study joins an ever growing pile showing that spanking is a risk factor to children's development," she said.

She pointed out that the findings on decreased vocabulary were also interesting, although, again, not very surprising ― except that it was only found with paternal spanking.

"There haven't been many studies that have looked at fathers' physical punishment. So that's a unique feature of this study," said Dr. Durrant.

She and her colleagues published a story last year in the Canadian Medical Association Journal that synthesized 2 decades' worth of trends in research on physical punishment in children.

As reported at the time by Medscape Medical News, they found that this practice was associated with increased risk for aggression, antisocial behavior, substance abuse, and mental illness in the kids.

Dr. Durrant added that it would have been nice if the authors of the current study had included an additional measure of parental spanking practices instead of relying just on parental recall, because that may have led to the underestimating of actual rates.

However, she said the study is a strong addition to the literature.

"In summary, the overall findings were not surprising, but this study addressed many of the questions that are raised about different variables that could be confounding the relationship and saw that the relationship held over a longer period of time than people have been able to look at before."

The study was funded by the National Institute of Child Health and Human Development, the National Science Foundation, the US Department of Health and Human Services, and the National Institutes of Health. The study authors and Dr. Durrant have disclosed no relevant financial relationships.

Pediatrics. Published online October 21, 2013. Full article

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