"One in 8 American children, at some point between birth and their 18th birthday, will be maltreated," said study researcher Christopher Wildeman, associate professor of sociology at Yale University.
Although the percentage of confirmed cases of abuse and neglect is lower than 25 years ago, it's higher than Wildeman had anticipated. "We compulsively checked our numbers when it came back as 12 percent," he said.
The study, published online June 2 in JAMA Pediatrics, used information from the National Child Abuse and Neglect Data System Child File. The database contains only confirmed reports of maltreatment.
The researchers defined confirmed maltreatment as "any report that was substantiated or indicated, meaning sufficient evidence existed for [child protective services] to conclude that abuse or neglect had occurred."
More girls were mistreated than boys (13 percent versus 12 percent), and certain minority groups were more prone to abuse than others, the researchers said.
More than 20 percent of black children are mistreated, they found. "For Native Americans, the risk is closer to 15 percent," Wildeman said.
For Hispanic children, the percentage is about 13 percent and for whites, close to 11 percent. "Asians had the lowest, at about 3 to 4 percent," he said.
Risk is highest early in life, with 2 percent of children having a confirmed report by their first birthday, and nearly 6 percent by their fifth birthday, the researchers said.
However, fewer children suffer abuse now compared to several decades ago, Wildeman said. "There have been big declines in child maltreatment in the U.S. in roughly the last 25 years," he said, citing other research.
About 80 percent of the cases the team evaluated were neglect, not abuse, he said.
The researchers tracked cases for the years 2004 through 2011, which included about 5.6 million children. They then estimated the cumulative prevalence of confirmed maltreatment by age 18.
The new numbers don't surprise Janet Currie, a professor of economics and public affairs at Princeton University in New Jersey. "Child maltreatment is a huge and underappreciated public health problem," said Currie, who was not involved in the study.
In her own recent research, she found that child maltreatment is the leading cause of death from injuries in children older than 1 year.
Because the new report only focuses on confirmed cases, she said it might underestimate the scope of the problem. "Cases may not be confirmed for various reasons, including lack of child welfare staff available to investigate a report,'" she said.
Anyone who suspects a child is mistreated should notify their local or state child protective services or police department, experts say. "Many suspected cases are not verified, but it is better to be safe than sorry about this," she added.
Telltale signs of abuse include unexplained bruises or burns; fear of going home; age-inappropriate behaviors such as thumb-sucking or bed-wetting, or inappropriate sexual behaviors. A child who is chronically unwashed may be neglected. Other signs of possible neglect are lack of medical or dental care or drug or alcohol abuse, experts say.
To reduce the risk of mistreatment, friends and family should be especially attentive to the needs of parents of very young children, Wildeman said. "The risk of childhood maltreatment is about four times higher in the first year than any other age," he said, citing his research.
Having loved ones pitch in during that time might ease the burden and the stress, Wildeman said.
Safe Horizon has more about child abuse.