ADHD Cases on the Rise in US

Attention deficit hyperactivity disorder, or ADHD, is on the rise, with nearly one in 10 American children receiving an ADHD diagnosis, according to a new study from the U.S. Centers for Disease Control and Prevention.

"ADHD continues to increase, and that has implications for educational and health care because kids with ADHD disproportionately use more services, and there are several co-morbid conditions that go along with it," Dr. Lara J. Akinbami, lead author of the study, told ABCNews.com.

From 1998 to 2009, according to the study, the percentage of children ever diagnosed with ADHD increased from 7 percent to 9 percent. The study also found a larger increase in ADHD among children in the South and Midwest regions of the U.S.

ADHD is one of the most common behavioral problems in children, characterized by difficulty in sustaining attention, impulsivity and hyperactivity. It continues to occur more frequently in boys than girls, and the number of cases increased by about 10 percent in children living in low-income households.

"ADHD is genetically based and often unnoticed," said Michael Manos, head of the Center for Pediatric Behavioral Health at the Cleveland Clinic. "We're far better at noticing it now, and that is good."

But researchers say it's not clear whether the number of reported cases of ADHD has actually increased or whether there's simply more awareness of the disorder.

"Most informed professionals will concur that it is better reported and recognized. This fact has resulted in the prevalence increases," said Manos.

Every major ethnic group saw an increase in ADHD except for children of Mexican descent.

"Mexican children remain with much lower ADHD prevalence than other Hispanics," said Akinbami. "We tend to miss the differences between Puerto Ricans and Mexicans, and this difference could be largely due to remaining language behaviors and cultural attitudes. Whether this is a real lower prevalence or if it remains unreported is unclear."

Past research shows that only about half of children who qualify for an ADHD test actually receive one, researchers noted in the study.

"With prevalence rates so high across sex and race, and with the barriers that limit treatment in low-income families, we do a disservice to a large percentage of our population," said Manos.

"There are ways of making the world work for people with ADHD, people whose attention functions serve other purposes than those required in school," continued Manos. "If we got serious, we would completely alter how we teach children to learn. If we created educational programs that work for children and youth with ADHD, we would create educational programs that work for everyone."