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Parents who hit their kids may believe that a swat “just gets their attention” or imposes old-fashioned discipline, but spanking in fact makes behavior worse than it was before and can cause long-term harm, pediatricians said Monday.

The American Academy of Pediatrics strengthened its advice against corporal punishment in update guidelines, saying it makes kids more aggressive and raises the risk of mental health issues.

“Experiencing corporal punishment makes it more, not less, likely that children will be defiant and aggressive in the future,” the group says in its new guidelines to pediatricians.

“There’s no benefit to spanking,” said Dr. Robert Sege of Tufts Medical Center in Boston, who helped write the guidelines.

“We know that children grow and develop better with positive role modeling and by setting healthy limits. We can do better.”

Today, @AmerAcadPeds put out a new policy against spanking. Spanking and harsh words are harmful and don't work. Here are 10 other ways to discipline your child: https://t.co/69y8aE9dta #AAP18 pic.twitter.com/ZliESNugjL — HealthyChildren (@healthychildren) November 5, 2018

Verbal abuse and humiliation is also counterproductive, the pediatrics group said.

“Parents, other caregivers, and adults interacting with children and adolescents should not use corporal punishment (including hitting and spanking), either in anger or as a punishment for or consequence of misbehavior, nor should they use any disciplinary strategy, including verbal abuse, that causes shame or humiliation,” the group says in the updated guidelines.

"Within a few minutes, children are often back to their original behavior. It certainly doesn’t teach children self-regulation," Sege told NBC News.

"Techniques such as time out and other effective forms of punishment, the goal is to teach the child to regulate herself, so that she will have the ability to control and manage her own behavior. And that’s what it really is all about."

Americans still strongly believe in beating, spanking or paddling children, both at home and in school.

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“According to a 2004 survey, approximately two-thirds of parents of young children reported using some sort of physical punishment,” the pediatrics group said.

“These parents reported that by fifth grade, 80 percent of children had been physically punished, and 85 percent of teenagers reported exposure to physical punishment, with 51 percent having been hit with a belt or similar object.”

And in 2013, a Harris Interactive poll found that 70 percent of parents agreed with the statement that “good, hard spanking is sometimes necessary to discipline a child,” although that’s down from 84 percent of parents in 1986.

But things are changing, Sege said.

"If you limit your surveys to people who have a child aged 5 years and younger in their homes, who are a new generation of parents, most of them don’t like to spank their children and often don’t spank their children," he said. "We think there’s a generational shift where today’s parents are much less likely to spank their children than their parents were."

One group studied parents in their home and found most parents did give kids a verbal warning before physically striking out. But they did not wait long. “Corporal punishment then occurred at a mean of 30 seconds later, suggesting that parents may have been ‘responding either impulsively or emotionally rather than instrumentally and intentionally,’” the pediatrics group said.

It did little good.

“The effects of corporal punishment were transient: within 10 minutes, most children (73 percent) had resumed the same behavior for which they had been punished.”

Not only does hitting kids do little good; it can worsen their long-term behavior.

“Children who experience repeated use of corporal punishment tend to develop more aggressive behaviors, increased aggression in school, and an increased risk of mental health disorders and cognitive problems,” Sege said in a statement.

That held even when parents were otherwise warm and loving.

Parents who hit their children often have serious problems of their own. “Parents who suffer from depression tended to use corporal punishment more frequently. In addition, family economic challenges, mental health problems, intimate partner violence and substance abuse all are associated with increased reliance on corporal punishment,” Sege said.

“One small report suggested that parents who themselves have a history of trauma are more likely to use corporal punishment than other parents.”

So what can parents do instead?

“First, establish a positive, supporting and loving relationship with your child. Without this foundation, your child has no reason, other than fear, to demonstrate good behavior,” the AAP advises.

“Second, use positive reinforcement to increase the behavior you want from your child.”

Time outs work very well for younger children, the group said. “Discipline older children by temporarily removing favorite privileges, such as sports activities or playing with friends. If you have questions about disciplining your children, talk with your pediatrician,” it advises.

Pediatricians will almost always recommend discipline that does not include hitting children, or forcing them to eat spices, washing their mouths out with soap or other abusive punishments. Only 6 percent of the 787 US pediatricians surveyed in 2016 approved of spanking, and only 2.5 percent actually expected it to do any good.

The American Psychological Association says positive reinforcement is more effective than spanking.

“Positive reinforcement for alternative behaviors is extremely effective,” it says.