WASHINGTON, DC— Evidence is mounting that ADHD is an independent, clinically meaningful comorbid condition in children with autism, Asperger’s syndrome, or other forms of pervasive developmental disorder.

Among the most recent support for this was a study comparing DSM-IV ADHD symptom subtypes in 483 children with and 326 children without pervasive developmental disorder. Lead author Kenneth D. Gadow, PhD, Professor in the Department of Psychiatry and Behavioral Science at the State University of New York at Stony Brook, presented the study findings at the 51st Annual Meeting of the American Academy of Child and Adolescent Psychiatry.

STRIKINGLY SIMILAR SUBTYPES

“The number of similarities between ADHD subtypes in pervasive developmental disorder and non–pervasive developmental disorder children was truly striking,” Dr. Gadow told Neuropsychiatry Reviews. “To begin with, children with pervasive developmental disorder who exhibited ADHD behaviors differed in important ways from children with pervasive developmental disorder who were not classified as having ADHD symptoms. Moreover, children with pervasive developmental disorder who were also classified as having ADHD, combined type, were the most impaired, at least with regard to co-occurring psychiatric symptoms and pervasive developmental disorder symptoms,” he explained. Children with the ADHD hyperactive-impulsive subtype were the least impaired. “These results are very similar to what we and others have found in non–pervasive developmental disorder children with ADHD,” he added.

Also, in both groups of children, the ADHD hyperactive-impulsive subtype was least common, the combined type was most often related to environmental adversity (eg, low socioeconomic status or being in a single-parent family), and oppositional and aggressive behavior were related more to hyperactivity than to inattention. These similarities suggest that at least some of the causes of ADHD may be the same in children with and without pervasive developmental disorder, said Dr. Gadow.

DEFYING CHANCE

“There is something else that just defies chance occurrence—the difference in the way that parents and teachers rated the severity of specific psychiatric symptoms in children with and without pervasive developmental disorder,” Dr. Gadow related. Specifically, their ratings showed the same pattern of divergence, and teacher ratings demonstrated greater diagnostic validity for ADHD.

The study was somewhat unique, he noted, in that the same DSM-IV assessment instrument was used to identify psychiatric and pervasive developmental disorder symptoms in both groups of children. “We did not use an autism scale of emotional and behavioral problems for the pervasive developmental disorder kids and a DSM-IV scale for the non–pervasive developmental disorder comparison group,” he pointed out. “Scientists tend to use a different instrument for the pervasive developmental disorder population, which makes comparison between studies of children with and without pervasive developmental disorder somewhat difficult.”

TREATMENT POSSIBILITIES

The study is positive from a treatment standpoint, because it raises the possibility that pediatric ADHD patients with pervasive developmental disorder might respond as well to methylphenidate as those without pervasive developmental disorder. It is frustrating that current findings indicate a somewhat less robust effect for children with autism, Dr. Gadow remarked—but he added that the issue has not been studied nearly enough for researchers to draw any final conclusions, especially with regard to variables that might predict a more favorable response to medication.

It is also possible, suggested Dr. Gadow, that children with both pervasive developmental disorder and ADHD may respond differently to certain types of behavioral intervention—or they may be at greater risk for long-term impairment than youngsters who do not exhibit ADHD behaviors. “If the latter is true, we should of course be targeting these children and possibly their families for greater and more intense intervention,” he said. “But at this juncture, this is all really a matter of speculation.”

—Timothy Begany

Suggested Reading
Gadow KD, DeVincent CJ, Pomeroy J, Azizian A. Psychiatric symptoms in preschool children with PDD and clinic and comparison samples. J Autism Dev Disord. 2004;34:379-393.
Yoshida Y, Uchiyama T. The clinical necessity for assessing attention-deficit/hyperactivity disorder (AD/HD) symptoms in children with high-functioning pervasive developmental disorder (PDD). Eur Child Adolesc Psychiatry. 2004;13:307-314.

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