High Proportion of Children With Autism Also Have ADHD

Pam Harrison

June 11, 2013

Nearly one third of children with autism spectrum disorder (ASD) also meet diagnostic criteria for attention-deficit/hyperactivity disorder (ADHD), new research suggests.

Rebecca Landa, PhD, and Patricia Rao, PhD, Center for Autism and Related Disorders, Kennedy Krieger Institute, Baltimore, Maryland, found that 29% of children between 4 and 8 years of age with ASD were rated by their parents as having clinically significant symptoms of ADHD on the basis of a standard assessment scale specifically designed to identify core ADHD symptoms.

Moreover, children with comorbid ASD and ADHD had lower cognitive functioning, more severe social impairment, and greater delays in adaptive functioning than children with ASD only.

"It is important to recognize that these two disorders can go together, because the presence of ADHD in children with ASD complicates children's learning," Dr. Landa told Medscape Medical News.

"And our article shows that if you have both disorders, you are at greater risk for having greater impairment, and you are going to need more support. This has implications for thinking about earlier detection of attentional abnormalities in autism and addressing these therapeutically."

The study was published online on June 5 in Autism: The International Journal of Research and Practice.

Cognitive Delay

A total of 162 children (mean age, 5.6 years) were included in the study. Children were first divided into ASD and no-ASD groups.

They were then further categorized according to parent-reported symptoms of ADHD on the Hyperactivity and Attention Problems subscales of the Behavior Assessment System for Children–Second Edition.

"We found that a significantly higher percentage of children with comorbid ASD + ADHD were classified as having significant cognitive delays (low functioning autism) than children with ASD only (61% vs 25%)," the authors write.

Parents also rated children with both disorders as being significantly more likely to have stereotypic and repetitive behaviors than children with ASD alone.

The fourth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) states that ASD and ADHD cannot be codiagnosed.

However, the study's investigators believe there will be some abnormalities in an ASD child's social attention but that these abnormalities should not affect multiple aspects of the child's attention.

"In the new DSM-5, it is now recognized that you can have both disorders," Dr. Landa noted, "and the recent change to the DSM-5 to remove the prohibition of a dual diagnosis of autism and ADHD is an important step forward."

Asked by Medscape Medical News to comment on the study, Deborah Fein, PhD, University of Connecticut, in Storrs, said that she was "very impressed" with its findings.

"The study quantifies what clinicians have observed for a long time — that children with ASD who have particular difficulties with attention, even meeting criteria for ADHD, have more severe challenges in learning and tend to be lower functioning."

Like Dr. Landa, Dr. Fein also noted that dual diagnosis is now permissible in the new DSM-5.

"This is particularly important since it may lead to behavioral supports for better attention and possible medication trials that might not otherwise have been attempted," Dr. Fein stated.

The study was supported by the National Institute of Mental Health. Dr. Landa and Dr. Fein report no relevant financial relationships.

Autism. Published online June 5, 2013. Abstract


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