THURSDAY, March 26, 2015 (HealthDay News) -- Conventional wisdom says that abused children often grow up to be abusive parents, but a 30-year study of American families suggests it's more complicated than that.
In one striking finding, researchers uncovered little evidence that physical abuse is passed from one generation to the next.
"That was extremely surprising," said lead researcher Cathy Spatz Widom, a professor of psychology at John Jay College of Criminal Justice, in New York City. "The theory has been that children of parents who were abused are at increased risk of physical abuse."
That theory has been supported by past research. But, Widom explained, those studies have been hampered by limitations, such as working "backward" -- starting with parents accused of abuse, and asking them if they'd been mistreated as kids.
"The problem there is, you miss the parents who were abused but did not go on to have these issues," Widom explained.
Her study, published in the March 27 issue of Science, followed two generations of families, including over 1,100 parents and their kids. More than half of the parents had been abused or neglected as children, back in the 1960s and 1970s; the rest had no history of abuse, but were from similar backgrounds.
To see whether the children of abused parents were at risk, Widom's team used three sources: Records from child protective services (CPS); interviews with parents; and interviews with their children once they were young adults.
Overall, the researchers found, children of abused parents were at no greater risk of physical abuse. And that was true whether the information came from parents' or children's reports, or CPS records.
Based on CPS reports, for example, almost 7 percent of kids born to abused parents suffered physical abuse, versus just over 5 percent of the comparison group -- a difference that was not statistically significant.
In contrast, children of abused parents were at higher risk of sexual abuse or neglect, the finding showed.
There's no clear explanation for the difference between physical abuse and other forms of mistreatment, according to Widom.
"It's really puzzling to us," she said. "We need more research to dig into the reasons."
Dr. Kristine Campbell, a pediatrician who studies child abuse, commended the work.
"This is a very impressive research effort," said Campbell, an associate professor at the University of Utah, in Salt Lake City.
"There has long been acceptance that abuse is passed down through generations, almost like eye color or skin tone," Campbell said.
In her personal experience, she added, "I've seen this presented as a reason to suspect a parent of abusing a child. I've also seen parents terrified that they are predestined to abuse their child because of their own histories of maltreatment."
But these findings show that's not the case, Campbell said.
Widom agreed. "Parents shouldn't feel they're doomed to continuing the cycle of abuse," she said.
Her team did, however, find that authorities may have a "bias" toward detecting abuse when parents have a history of child mistreatment.
The researchers looked at the rate of official CPS reports among all parents and kids who reported abuse or neglect: When it came to families where parents had been abused, about 30 percent of abuse cases involved an official CPS report; among other families, CPS picked up only 15 percent of abuse cases.
How would that happen? Widom speculated that parents with a history of child abuse may use more social services in general.
"Each time you're in contact with social services," Widom said, "there's an opportunity to be observed by the people working for those agencies, and they're mandated to report suspected child abuse."
But that does not mean abuse is "over-detected" in those families, Campbell stressed. Instead, she said, the findings imply that the system often misses child mistreatment -- especially in families where parents have no history of abuse.
Despite that sobering take-away, Campbell also saw "good news" in the findings.
"The substantial majority of parents who have experienced child abuse will never abuse their own children," Campbell said.
And for those struggling to get past their childhood mistreatment, many communities have programs that help young moms and dads build their parenting skills, she added.
According to Widom, future studies should dig for the reasons why some abused kids become abusive parents, while many others do not.
Campbell agreed. "If we want to work on child abuse prevention, we need to better understand the perpetrators of abuse," she said. "My experience is that very few parents who abuse their children can simply be dismissed as 'monsters.'"
The U.S. Department of Health and Human Services has more on child abuse prevention.