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By Genevra Pittman

NEW YORK -- Think spanking will help teach an out-of-control child to stay in line? A new study suggests the opposite may be true.

Researchers found kids who were spanked as 5-year-olds were slightly more likely to be aggressive and break rules later in elementary school.

Those results are in keeping with past research, said Elizabeth Gershoff. She studies parental discipline and its effects at the University of Texas at Austin.

"There's just no evidence that spanking is good for kids," she told Reuters Health.

"Spanking models aggression as a way of solving problems, that you can hit people and get what you want," said Gershoff, who wasn't involved in the new study.

"When (children) want another kid's toy, the parents haven't taught them how to use their words or how to negotiate."

Despite mounting evidence on the harms tied to spanking, it is "still a very typical experience" for U.S. children, the study's lead author said.

"Most kids experience spanking at least some point in time," said Michael MacKenzie of Columbia University in New York. "So there's this disconnect."

His team used data from a long-term study of children born in one of 20 U.S. cities between 1998 and 2000. The new report includes about 1,900 kids.

Researchers surveyed parents when children were 3- and 5-years-old about whether and how often they spanked their child.

A total of 57 percent of mothers and 40 percent of fathers said they spanked children when they were 3 years old. That fell slightly to 52 percent of mothers and 33 percent of fathers who spanked at age 5.

Children acted out more and were more aggressive when they had been spanked by their mothers as 5-year-olds, whether regularly or occasionally.

Spanking by mothers at least twice a week was tied to a two-point increase on a 70-point scale of problem behavior. That was after the researchers took into account children's behavior at younger ages and other family characteristics.

There was no link between spanking by parents at age 3 and children's later behavior, however.

Kids also tended to score lower on vocabulary tests when they had been regularly spanked by their fathers at age 5, MacKenzie and his colleagues write in Pediatrics.

It's possible that parents who are spanking are not talking to their children as often, Gershoff said. Or kids who are spanked and act out could be more distracted in the classroom.

When it comes to disciplining children, she said there's more evidence on what doesn't work long-term than what does.

"We know that spanking doesn't work, we know that yelling doesn't work," Gershoff said. "Timeout is kind of a mixed bag. We know that reasoning does work."

MacKenzie said spanking continues to seem effective to parents in the short term, which makes it hard to change their minds about it.

"It's strongly associated with immediate compliance," he told Reuters Health. "Children will change their behavior in the moment."

Because family strain and spanking often go together, he said doctors should try to support stressed parents to encourage more positive forms of discipline.

"The techniques that are designed to promote positive behaviors … oftentimes take more effort and time to put into place," MacKenzie said.