A report from the federal Centers for Disease Control and Prevention finds that the percentage of U.S. children diagnosed with attention deficit hyperactivity disorder, or ADHD, increased from about 7 percent in 1998 to 9 percent by 2009.
Children with ADHD have trouble paying attention, may sometimes act impulsively, and may be overly active, the CDC notes.
Boys are still more likely than girls to be diagnosed, but diagnoses for both genders have increased, with about 12 percent of boys and 6 percent of girls now carrying the ADHD label.
The study also found that prevalence differences among children of different races narrowed from 1998 to 2009. Researchers also noted that ADHD was more common among children with lower family incomes than among those with family incomes 200 percent or more above the federal poverty level.
The findings are drawn from a nationally representative federal survey of about 40,000 American households.
A version of this article appeared in the August 31, 2011 edition of Education Week as ADHD Students