Fifty years of research on spanking children has concluded that the more children are spanked, the more likely they are to defy their parents and experience increased anti-social behaviour, aggression, mental health problems and cognitive difficulties.

The analysis used systematic qualitative and quantitative methods by experts at the University of Texas at Austin and the University of Michigan to examine five decades of research involving more than 160,000 children.

The researchers call it the most complete analysis to date of the outcomes associated with spanking, and more specific to the effects of spanking alone than previous papers, which included other types of physical punishment in their analyses.

“Our analysis focuses on what most Americans would recognize as spanking and not on potentially abusive behaviours,” says Elizabeth Gershoff, associate professor of human development and family sciences at the University of Texas at Austin.

“We found that spanking was associated with unintended detrimental outcomes and was not associated with more immediate or long-term compliance, which are parents’ intended outcomes when they discipline their children.”

Gershoff and co-author Andrew Grogan-Kaylor, an associate professor at the University of Michigan School of Social Work, found that spanking (defined as an open-handed hit on the behind or extremities) was significantly linked with 13 of the 17 outcomes they examined, all in the direction of detrimental outcomes.

“The upshot of the study is that spanking increases the likelihood of a wide variety of undesired outcomes for children. Spanking thus does the opposite of what parents usually want it to do,” said Grogan-Kaylor.

Gershoff and Grogan-Kaylor tested for some long-term effects among adults who were spanked as children. The more they were spanked, the more likely they were to exhibit anti-social behaviour and to experience mental health problems.

They were also more likely to support physical punishment for their own children, which highlights one of the key ways that attitudes toward physical punishment are passed from generation to generation.

The researchers looked at a wide range of studies and noted that spanking was associated with negative outcomes consistently and across all types of studies, including those using the strongest methodologies such as longitudinal or experimental designs.

As many as 80% of parents worldwide spank their children, including many in the Caribbean, according to a 2014 UNICEF report.

Gershoff notes that this persistence of spanking is despite the fact there is no clear evidence of positive effects from spanking and ample evidence that it poses a risk of harm to children’s behaviour and development.

Both spanking and physical abuse were associated with the same detrimental child outcomes in the same direction and nearly the same strength.

“We as a society think of spanking and physical abuse as distinct behaviours,” she says. “Yet our research shows that spanking is linked with the same negative child outcomes as abuse, just to a slightly lesser degree.”

The study results are consistent with a report released recently by the Centres for Disease Control and Prevention that called for “public engagement and education campaigns and legislative approaches to reduce corporal punishment,” including spanking, as a means of reducing physical child abuse.

Gershoff added: “We hope that our study can help educate parents about the potential harms of spanking and prompt them to try positive and non-punitive forms of discipline.”

An earlier study by researchers at the University of Michigan found that 30% of one-year-old children were spanked at least once in the past month by their mother, father or both parents.

A long-time topic of debate, spanking children is a common practice among U.S. parents. Previous research has focused on disciplining children as young as age three, in part because spanking is common among children of this age.

Researchers examined 2,788 families who participated in a longitudinal study of new births in urban areas. The study indicated that spanking by the child’s mother, father or mother’s current partner when the child was a year old was linked to Child Protective Services’ involvement between ages one and five. During that time, 10% of the families received at least one visit by Child Protective Services.

Social work professors Shawna Lee and Grogan-Kaylor say spanking babies is particularly misguided and potentially harmful, and may set off a cascade of inappropriate parental behaviour.