By the time they reach age 18, about 12 percent of US children will experience neglect, physical, sexual, or emotional abuse, according to new research from Yale University.

Although the number of confirmed cases of abuse and neglect is lower than 25 years ago, lead author Christopher Wildeman was still surprised by the results. And not all cases are typically reported - prior to this study, it was believed that one in 100 children were affected by maltreatment, not one in eight, according to the press release.

Results showed that minority children suffer most, with one in five black children and one in seven Native American children experiencing maltreatment during the study period. And a Health Day report noted that girls were more prone to mistreatment than boys.

"The risk of childhood maltreatment is about four times higher in the first year than any other age," Wildeman also noted.

For the study, authors used the National Child Abuse and Neglect Data System Child File, which includes information on all US children with a confirmed report of maltreatment.

The findings revealed that over 5.6 million children had experienced maltreatment between 2004 and 2011.

"Confirmed child maltreatment is dramatically underestimated in this country. Our findings show that it is far more prevalent than the 1 in 100 that is currently reported," Wildeman, Yale associate professor of sociology and faculty fellow at the Institution for Social and Policy Studies, said in the press release.

State and local agencies are to blame for the discrepancy it seems. Such facilities receive over three million maltreatment referrals each year, the US Centers for Disease Control and Prevention reported, and yet not all cases are realized.

"Child maltreatment is a huge and underappreciated public health problem," Janet Currie, a professor of economics and public affairs at Princeton University, who was not involved in the study, told Health Day.

Anyone who suspects a child is being mistreated should notify their local or state child protective services or police department, experts say. Telltale signs include unexplained bruising or burns, fear of going home, inappropriate behavior, and drug or alcohol abuse.

The findings were published in the journal JAMA Pediatrics.