Two important reports regarding ADHD in kids came out in recent days, including a study by Mayo Clinic researchers in Rochester, Minn., that found a high prevalence of hyperactive children who also had writing problems.

Dr. Kouichi Yoshimasu and Mayo colleagues studied 5,718 children -- born between 1976 and 1982 and raised in the Rochester area -- and found the rate of written-language disorder (WLD) to be much higher in kids with ADHD. For boys, 64.5% with ADHD had this type of learning disability compared to only 16.5% of boys without the disorder. For girls, the respective figures were 57% and 9.4% Researchers said the study, released Monday in the journal Pediatrics, underscores the need to screen kids with ADHD for learning disorders related to their reading abilities.

On Friday, the federal government reported a 30 percent increase over the past decade in the rate of children ages 5 to 17 diagnosed with ADHD, or Attention Deficit Hyperactivity Disorder. Based on parent surveys, the report indicated that 9 percent of U.S. kids were diagnosed with ADHD in 2007-2009, compared to 6.9 percent in 1998-2000.

The prevalence of ADHD was even higher among children whose families were living at or near poverty levels. Other disparities: ADHD was more common among white children and less common among Mexican children. In the Midwest, roughly 10.2 percent of children had received a diagnosis of ADHD as of 2007-2009.