TUESDAY, Aug. 23 , 2011 (HealthDay News) -- Children diagnosed with attention-deficit hyperactivity disorder (ADHD) have a much higher risk of developing a written language disorder, a new study indicates.
To ADHD experts, the current observation does not come as a particular surprise. It has long been known that children with ADHD stand a much higher chance of developing some form of learning disability -- especially a reading disability, which accounts for about 80 percent of all learning disabilities affecting ADHD patients.
But the new finding, say researchers, is the first evidence to support a specific link between ADHD and a writing disorder.
"Most of the ADHD research is based on a clinical research sample of children, which may not reflect the full spectrum of ADHD in the population at large," noted study co-author Dr. Slavica K. Katusic, an associate professor of epidemiology and pediatrics. "So this is the uniqueness of this study, because this is population-based."
"And what we found is that, regardless of gender, there is a dramatic difference" in the risk of written-language disorder, said Katusic, who is also a consultant in the Mayo Clinic's department of health sciences research in Rochester, Minn. "ADHD kids are at a five times greater risk for having writing problems compared to all others who do not have ADHD."
Katusic and her colleagues report the findings in the September issue of Pediatrics.
Just this week, a new U.S. Centers for Disease Control and Prevention survey reported that over the last decade the number of young Americans diagnosed with ADHD has been on the upswing. Whether this is a function of an actual increase in incidence or improved screening remains unclear.
What is clear is that ADHD is currently the most common behavioral disorder among children, with between 3 percent and 5 percent of school-aged Americans diagnosed with the condition, according to the National Institutes of Health.
ADHD patients tend to have difficulties maintaining focus and often express themselves through inappropriate impulsive and/or overactive behavior.
The authors note that WLD -- the acronym for written-language disorder -- is distinct from reading disabilities: The problems revolve around an impaired ability to express oneself through the written word.
In the case of WLD, the impairment may cause memory and organizational issues, as well as compromised handwriting and/or spelling.
To explore a possible link between ADHD and WLD, the authors focused on 5,718 children who had been born between 1976 and 1982 in Rochester, Minn.
The majority of the participants were white and middle-class. All were tracked from birth until roughly the age of 19.
Information about the children's ADHD status and learning disabilities was gleaned from medical records, as well as records drawn from public and private schools and private tutorial settings.
The results: by the age of 19 the risk for developing WLD was much higher among those boys and girls who had been diagnosed with ADHD than for those who had not.
Specifically, among boys, those with ADHD had a nearly 65 percent risk for having writing difficulties, compared to 16.5 percent among those without ADHD. Among girls, the figures were 57 percent vs. 9.4 percent.
In addition, for girls with ADHD who also had a reading disability, the risk of developing writing problems was significantly higher for girls than for boys with the same conditions.
However, for ADHD boys and girls who did not have a reading disability, the risk of having WLD was similar.
The authors said that their findings should reinforce standing recommendations issued by the American Academy of Pediatrics that children with ADHD be screened for coexisting disabilities, including written language disorders.
"When someone suspects that a child has ADHD, people are so impressed with concerns over dyslexia that they sometimes kind of forget about problems with writing," Katusic cautioned. "So, this should bring some needed attention to the need for equal testing and equal help for kids who also have writing problems."
Dr. Tanya Froehlich, a developmental and behavioral pediatric specialist and assistant professor of pediatrics at Cincinnati Children's Hospital Medical Center, noted the findings were not unusual.
"It's completely in line with what's expected and with prior research data," she said. "We already know that people with ADHD have a higher rate of reading disabilities. So this makes sense, and goes along with [prior research] as well as with what we have observed in clinic."
Another expert, Dr. Andrew Adesman, chief of developmental and behavioral pediatrics at the Cohen Children's Medical Center in New Hyde Park, N.Y., concurred.
"It's not surprising, because we know that ADHD children will likely have a learning disability. And we know that writing disability is a form of that," he said. "But it's important nonetheless to have confirmation in a study as strong as this."
More information
For more on ADHD, visit the National Institutes of Health.
