Two decades after it recommended against spanking children, the Illinois-based American Academy of Pediatrics has beefed-up its advice on the subject, saying corporal punishment — and verbal abuse — can harm kids.

“The good news is, fewer parents support the use of spanking than they did in the past,” Dr. Robert D. Sege, one of the authors of the academy’s latest statement. “Yet corporal punishment remains legal in many states, despite evidence that it harms kids — not only physically and mentally, but in how they perform at school and how they interact with other children.”

The academy’s 1998 statement discouraged parents from spanking their kids, but the new statement — posted online Monday and set to be published in the December issue of Pediatrics — draws upon 20 years of research to bolster that position.

The research found, among other things, that, over time, spanking often leads to more aggressive behavior in kids. Another study links prolonged spanking to reduced development in the part of the brain that controls and regulates emotions. A different study found that within 10 minutes of a spanking, 73 percent of children resumed the behavior for which they’d been punished.

Marc S. Atkins, a professor of psychiatry and psychology at U.I.C.’s Institute for Juvenile Research, says when a parent spanks a kid — say, for fighting with another child — it sends an unintended message: “‘Wait until you’re as big as me and then you can get away with it.’ The distinction between disciplining and then going out and beating somebody up because you don’t like them is not a distinction that is very clear to little kids.”

Atkins recommends a range of strategies instead of spanking, including being prepared for possible behavioral issues before they arise, such as bed-time tantrums. Offer a reward for good behavior, but keep it simple. He recalled one parent who bought a child a bicycle after the kid got up on time during his first week of school.

“What’s the problem? What are you going to do for week two?” Atkins said.

Parental spanking remains legal in the United States, although corporal punishment is outlawed in schools in 31 states, including Illinois.