A Recent study reveals there's an increase of U.S. children diagnosed with attention deficit hyperactivity disorder (ADHD). More than 10 percent of U.S. children are suffering from the disorder, most of which are girls and children from minority groups.

Experts say that the increase in diagnosis may have been the result of better screening and monitoring among previously under-diagnosed groups, NBC News reports. This is most notable among girls, Hispanics, and older children.

Around 5.8 million children aged five to 17 are diagnosed with ADHD. The disorder is characterized by social and behavioural problems, and difficulty in school. This is the analysis of cases reported by parents from 2003 to 2011.

From 8.4 percent in 2003, the diagnosis rates leaped to 12 percent by 2011; that's 43 percent overall increase during the study. At the time of the study, the diagnosis among girls jumped from 4.7 percent in 2003 to 7.3 percent in 2011; that almost 55 percent increase. However, the disorder is still prevalent among boys.

"The sharper increase among girls was a surprise primarily because ADHD is typically diagnosed among boys," said study co-author Sean Cleary, a public health researcher at George Washington University in Washington, D.C.

"One possibility to explain the increasing trend among females is a greater recognition of ADHD symptoms observed (e.g. withdrawn, internalizing) that are traditionally overlooked because they are not typically considered a sign of this condition," Cleary added by email.

Cleary and co-author Kevin Collins of Mathematic Policy Research analyzed data on more than 190,000 children from U.S. surveys done in 2003, 2007 and 2011. Parents report whether their child had been diagnosed with ADHD. Boys still accounted for most cases which increased to 16.5 percent in 2011; that's a 40 percent increase from the previous years.

Also, diagnosis among Hispanic children rose 83 percent and for African-American, it jumped 58 percent. Still, the majority of cases are still made up of white children.

However, the findings are not at all surprising and are actually consistent with the trends doctors have been seeing for years. Further studies are needed to address why the children were diagnosed and the appropriate treatments for them.