Thu, Feb 28, 2008 (HealthDay News) — Researchers have uncovered another damaging consequence of spanking: risky sexual behaviors, or even sexual deviancy, when the child grows up.

"This adds one more harmful side effect to spanking," said Murray Straus, a spanking expert who was expected to present the findings of four studies at the American Psychological Association's Summit on Violence and Abuse in Relationships in Bethesda, Md., on Thursday.

"I think that it's pretty powerful," said Elizabeth Gershoff, an assistant professor at the University of Michigan's School of Social Work. "It's across several studies and across different forms of either risky or deviant sexual behavior."

Straus, who was the author of all four studies, hopes the findings will raise awareness among child development experts.

"My hope is to convince my colleagues that they ought to put this in their textbooks," said Straus, co-director of the Family Research Laboratory at the University of New Hampshire, in Durham. "It's amazing. Something experienced by all American kids gets an average of half a page in child development textbooks, and not a single one comes to the conclusion that parents should never spank."

Even the revered Dr. Spock, who was anti-spanking, never came right out and advised parents outright not to do it, he added. Instead, Spock advised "avoiding it if you can."

A meta-analysis of spanking studies conducted by Gershoff found 93 percent agreement among studies that spanking can lead to such problems as delinquent and anti-social behavior in childhood along with aggression, criminal and anti-social behavior and spousal or child abuse as an adult.

"There's probably nothing else in child development that has 93 percent agreement in results," Straus said.

Five percent of people who have never been spanked hit their partners, versus 25 percent of those who were spanked frequently.

However, some 90 percent of U.S. parents spank toddlers, according to Straus.

The review being presented at the meeting are the first to look at the relationship of spanking to sexual behavior.

They found that spanking and other corporal punishment is associated with an increased probability of verbally and physically coercing a dating partner to have sex; risky sex such as premarital sex without using a condom; and masochistic sex such as spanking during sex.

There is a "dose response" at work here. "The more parents spank, the higher the probability of harmful side effects," Straus noted.

Of course, there's a similar dose response for smokers. But if someone reaches the age of 65 without developing lung cancer, it doesn't mean that smoking isn't harmful. It means the person was one of the lucky ones.

It's the same with spanking, Straus said. "If a person says, 'I was spanked, and I don't have any interest in bondage and discipline sex, that's correct, but it's not because spanking is OK, it's because they're one of the lucky ones."

And spanking a child once may be like picking up that first cigarette. "The trouble is, if you have a 2-year-old, you pretty soon decide you can't avoid it. The recidivism rate for whatever 'crime' you correct a 2-year-old for is about 50 percent in two hours."

"I've been researching corporal punishment for 30 years and, in the course of that time, the evidence has accumulated that it doesn't work any better than non-corporal punishment but has harmful side effects. I have come to the conclusion that parents should never, ever spank because, although it does work, it's no better than non-hitting methods that don't have harmful side effects. If there was an FDA for spanking, they'd say use an alternative that doesn't have harmful side effects."