Physical punishment of children, such as spanking, is increasingly linked with long-term adverse consequences, researchers wrote.
An analysis of research conducted since the 1990 adoption of the UN's Convention on the Rights of the Child suggests that no studies have found positive consequences of physical punishment, according to Joan Durrant of the University of Manitoba in Winnipeg, and Ron Ensom of the Children's Hospital of Eastern Ontario in Ottawa.
While some studies have found little effect either way, most research has uncovered a range of negative outcomes, including increased aggression and later delinquency, Durrant and Ensom wrote online in CMAJ.
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The clinical implication, they suggested, is that doctors who are familiar with the research can help parents find more constructive ways of providing discipline.
"In doing so, physicians strengthen child well-being and parent–child relationships at the population level," they wrote.
They noted that as recently as 1992, physical punishment of children was widely accepted, thought of as distinct from abuse, and considered "appropriate" as a way of eliciting desired behavior.
But research under way at that time was beginning to draw links between physical punishment and aggression in childhood, later delinquency, and spousal assault.
One important question was the direction of causality: Did aggressive, difficult children get punished or did punishment lead to aggression?
Large prospective studies in the mid- to-late 1990s, controlling for children's antisocial behavior and a host of other possible confounders, showed that physical punishment predicted later antisocial behavior.
And in a randomized trial of an intervention designed to reduce difficult behavior, parents were trained to reduce the use of physical punishment. The parental behavior changes were paralleled by a significant drop in difficult behavior in the children, Durrant and Ensom noted.
Later research showed associations between physical punishment and mental health, the risk of physical injury, poor parent-child relationships, and family violence in adulthood, they added.
Physical punishment has been linked with a variety of psychiatric disorders in children and adults, including depression, anxiety, and drug and alcohol abuse. More recent research suggests physical punishment slows cognitive development and hampers academic achievement.
As well, neuroimaging research suggests physical punishment actually reduces the volume of grey matter in regions associated with performance on intelligence tests, as well as causing alterations in dopaminergic regions linked to drug and alcohol abuse.
The mounting research has led professional organizations to look askance at physical punishment. The Canadian Pediatric Society, Durrant and Ensom noted, "strongly discourages" it, while the American Academy of Pediatrics (AAP) says "corporal punishment is of limited effectiveness and has potentially deleterious side effects."
The AAP recommends that physicians encourage parents to find other ways of maintaining discipline.
"Physicians have a primary responsibility for translating research and evidence into guidance for parents and children," the researchers concluded, "and they are credible and influential voices for advancing public education and policy concerning population health."
They can educate parents on what childhood behaviors are typical, suggest different approaches, and, if needed, refer patients to programs that will help them improve parenting skills.