A new study on spanking, considered the most complete analysis to date on the topic, finds the more children are spanked, the more likely they are to defy their parents, exhibit anti-social behaviors and experience mental health and cognitive problems.

“Spanking makes children’s behavior worse,” lead author Elizabeth T. Gershoff told me. “It has the opposite effect than what parents want: It doesn’t make children better-behaved, and it doesn’t teach children right from wrong. It’s not related to immediate compliance, and it doesn’t make children behave better in the future.”

Gershoff, an associate professor of human development and family sciences at the University of Texas at Austin, partnered with Andrew Grogan-Kaylor, an associate professor at the University of Michigan School of Social Work, to analyze 50 years of research on spanking.

“The evidence against spanking is one of the most consistent findings in the field of psychology,” Gershoff said.

Indeed, much of the new study’s findings have been reported before: Across age groups, spanking is an ineffective discipline tool that is associated with increased aggression, delinquent behaviors, anxiety and depression. Children who are spanked are also far more likely to spank their own children, continuing the pointless and barbaric cycle.

Gershoff and Grogan-Kaylor’s research, published in April’s Journal of Family Psychology, is distinct from similar studies in that it analyzes the effects of spanking alone, rather than including other types of physical punishment.

“We took all the data that focuses just on spanking, which we defined as swatting a child on the behind with an open hand,” Gershoff said.

That’s enough, they found, to cause long-term damage to a child’s psyche.

Still, roughly 80 percent of children around the world are spanked or otherwise physically punished, according to a 2014 UNICEF report.

Why the disconnect?

Gershoff chalks it up to a variety of factors — religious beliefs, the false belief that spanking is effective and, most frequently, the fact that parents were spanked as children.

“I have a couple of answers I give to people who think, ‘My parents spanked me, and I turned out OK,’ ” Gershoff said.

“First, we turned out OK because our parents did other things, like sat us down at the kitchen table and talked to us and gave us reasons why they wanted to see us behave. We turned out OK in spite of spanking, not because of it,” she said. “Second, when I was a child, there were no seat belts in cars. Do I think I turned out OK because my parents didn’t put me in a seat belt? No. I think I turned out because we didn’t get in an accident.

“We have evolved in our understanding of what protects children,” she said. “We now know we can protect our children and promote their behavior without spanking.”

I asked Gershoff if she thinks we’ll ever see spanking outlawed in the United States. It’s illegal, after all, to slug your spouse. Why not your children, who are, arguably, even more vulnerable?

“Society used to look the other way when spouses engaged in violence,” she said. “The women’s movement changed that. We had a big sea change, and it became illegal. We could see a sea change like that for children, and I hope that we will.”

Corporal punishment is banned in close to 50 countries, including Germany, Spain, Kenya, Denmark and the Democratic Republic of Congo. Why not here?

“It’s based on our history of treating children as property,” psychiatrist Paul Holinger, founder of Chicago’s Center for Child and Adolescent Psychotherapy, once told me. “And a misunderstanding of our basic built-in feelings and what gets elicited (from spanking) — the fear, the shame, the rage, the distress — which are neurobiologically toxic reactions.”

I hope this new study inspires a closer look at the cruel, outdated and, by all measures, ineffective practice.