WINNIPEG, Manitoba, Feb. 10 (UPI) -- A review of some 80 studies found spanking was associated with higher levels of aggression almost without exception, Canadian researchers said.
Joan Durrant, a child clinical psychologist at the University of Manitoba, and Ron Ensom of Ottawa's Children's Hospital of Eastern Ontario said of the research that spanned 20 years not one of the studies found any positive long-term effects associated with spanking -- but most found long-term negative effects.
The study, published in the Canadian Medical Association Journal, found spanking predicted later antisocial behavior, including delinquency and spousal assault.
Early experiments showed pain elicits reflexive aggression, and an early modeling study found boys in the fifth grade who watched a 1-minute video of a boy being yelled at, shaken and spanked with a paddle for misbehaving showed more aggression. Boys who watched a 1-minute video of non-violent responses to misbehavior did not show more aggression, the researchers said.
Other research showed reduction in harsh discipline used by parents of boys at risk for antisocial behavior was followed by significant reductions in their children's aggression, the review said.
In other research, physical punishment was linked to slower cognitive development and adversely affected academic achievement, the researchers said.
Rummaging studies suggested physical punishment might reduce the volume of the brain's gray matter in areas associated with performance on intelligence tests, while other studies indicated physical punishment could cause alterations in the parts of the brain associated with vulnerability to the abuse of drugs and alcohol, the review said.