Kids with attention-deficit hyperactivity disorder are more likely to have writing problems such as poor spelling and grammar than their peers, suggests a new study. And the difference may be especially conspicuous in girls with ADHD.

Reading and math problems often raise red flags for teachers and parents, but “written-language disorder is kind of overlooked,” said study author Dr. Slavica Katusic, from the Mayo Clinic in Rochester, Minnesota.

Writing “is a critical skill for academic success, social and behavioral well-being,” she added. And if writing problems aren’t noticed early on and addressed in kids with ADHD, they can suffer long into adulthood, Katusic told Reuters Health.

According to the Centers for Disease Control and Prevention, close to 10 percent of kids ages four to 17 in the U.S. have ever been diagnosed with ADHD - a number that has been on the rise in recent years.

The current study included close to 6,000 kids - everyone born in Rochester between 1976 and 1982 who was still living there after age 5. Katusic and her colleagues tracked school, tutoring and medical records to see which kids showed signs of ADHD, as well as how well they performed on writing, reading and general intelligence tests through high school.

In total, 379 of the kids fit the criteria for ADHD, which was more common in boys than girls, the study authors report in Pediatrics. Of all kids in the study, just over 800 scored poorly on tests of writing abilities. Most kids who had trouble with writing also had reading difficulties.

Writing problems were much more common in both boys and girls with ADHD. Close to two-thirds of boys with ADHD had trouble with writing, compared to one in six boys without ADHD.

For girls, 57 percent with ADHD had a writing problem, compared to less than 10 percent without ADHD. And girls with ADHD were almost ten times more likely to have a combination of writing and reading disorders compared to girls without the condition.

Memory and planning problems in kids with ADHD may affect the writing process, the authors explain, and ADHD has been linked to learning disorders in the past.

Annette Majnemer, who has studied handwriting in kids with ADHD at McGill University in Montreal, Canada, said that many with the disorder seem to have difficulty with that component of writing.

“It might be partially the fact that they’re inattentive and distractable and hyperactive,” she told Reuters Health. It’s also possible that motor skills and coordination problems are partly to blame, said Majnemer, who was not involved in the new research.

Katusic added that genetics might be behind both ADHD and some writing problems, but that in general, it’s very hard to tease out exactly how ADHD is linked to writing and reading disorders.

Treatment for the ADHD, as well as individual education plans that address some of those related difficulties, can help, Katusic said - especially if they’re started when problems first arise.

“When parents notice something or teachers notice something, (kids) have to be treated not only for ADHD, but they have to be tested to see if they have other learning problems,” she said.

“Clinicians and the teachers have to emphasize that the testing has to be done for everything, every kind of learning disability,” Katusic said. “It has to be identified early and the treatment has to start early.”

SOURCE: Pediatrics, online August 22, 2011.