A popular screening tool for attention-deficit hyperactivity disorder (ADHD) may be less accurate when a child has an autism spectrum disorder (ASD), according to a new study published in the Journal of Autism and Developmental Disorders.
This may result in children with ASD mistakenly being diagnosed with ADHD if their symptoms aren’t carefully traced to differentiate between social deficits or attention issues.
The researchers, including one of the psychologists who developed the ADHD screening tool — the ADHD Rating Scale Fourth Edition (ADHD-RS-IV) — say that the scale needs to be refined to better identify the correct disorder and that it should also be supplemented with careful clinical interviews.
“One of our best current screening measures for ADHD may be over-diagnosing ADHD in children with autism,” said study leader Benjamin E. Yerys, Ph.D., a researcher in the Center for Autism Research at Children’s Hospital of Philadelphia (CHOP).
“This is important because medications that work for ADHD may be less effective for a child on the autism spectrum.”
Scale scores are also used in recommending school-based services.
The study was conducted by researchers at CHOP, the Perelman School of Medicine at the University of Pennsylvania and Baylor University.
One complicating factor is comorbidity, as approximately 30 percent or more of children with ASD also have ADHD. The scale asks parents and teachers to provide numerical ratings regarding 18 items about a child’s behavior: nine items on inattention and nine on hyperactivity and impulsivity.
Study co-author Thomas J. Power, Ph.D., director of CHOP’s Center for Management of ADHD, developed ADHD-RS-IV in the 1990s (An updated version, the fifth edition, was published earlier this year, but not used in the current study).
“I’m excited to be involved in this study, and in efforts to refine our screening tools,” said Power, “especially since few researchers have previously investigated using this scale in children with ASD. Our research raises questions not only about this rating tool, but all such measures that rely on parent and teacher ratings to assess ADHD in children with ASD.”
For the study, the researchers analyzed ratings of 386 children, aged seven to 17, who had ASD without intellectual disability. To determine whether the tool was effective for children on the autism spectrum, the researchers used a method called factor analysis. They discovered that some questions on the ADHD rating scale were high for children with ASD instead of being high just for the subset of children who had significant ADHD symptoms.
“One underlying problem,” said Yerys, “may be in how we ask these questions.” For example, he explained, parents and teachers are asked “Does the child respond when spoken to directly?”
However, a simple yes or no to this question doesn’t distinguish between actual inattention (a symptom of ADHD) and a child’s lack of understanding about how to behave in a social situation (often found in ASD).
Similarly, other questions on the scale ask how well a child stays focused on one task during playtime. ADHD may cause a child to be easily distracted from an activity, but another child may instead stop playing because of ASD-related difficulties with social play.
“Until we’re able to develop and validate a new rating scale that takes symptoms of autism into account, parents who are concerned should seek out clinicians who are conducting evaluations for ADHD and are also taking into account the possibility of autism,” added Yerys.