ADHD May Be Over-Diagnosed in Children with Autism

Attention deficit hyperactivity disorder (ADHD) may be over-diagnosed in children with autism because of insufficient diagnostic tools, according to a new study from the Children's Hospital of Philadelphia.

Researchers examined the prevalence of children who meet ADHD criteria and their relationship to autistic characteristics in order to determine the validity of the diagnoses. The researchers mentioned in their study that both scientists and clinicians regularly use tools to assess ADHD comorbidity without empirical evidence that these measures are legitimate in children with autism, even though estimates say about a third of children with autism also have ADHD. The investigators included 386 children aged 7 to 17 years with autism, but without any intellectual disability, in their cohort, where they tested the ADHD Rating Scale Fourth Edition's efficacy (ADHD RS IV). The scale is designed so that parents and teachers provide input on 18 behavioral characteristics in the child: nine centered on inattention and nine focused on hyperactivity and/ or impulsivity.

"One of our best current screening measures for ADHD may be over-diagnosing ADHD in children with autism," study leader Benjamin E. Yerys, PhD, explained. "This is important because medications that work for ADHD may be less effective for a child on the autism spectrum."

The researchers suggested that the underlying problem with this diagnostic tool is the way the questions are asked. Yerys said that instead of asking "Does the child respond when spoken to directly?" may be better served differently, as a simple yes or no answer doesn't address the child's actual potential inattention (an ADHD characteristic) instead of an autistic behavior, such as the child not understanding how to act in social situations when responding to another individual. The study authors added that modifying a more nuanced scale to minimize the influence of autism on the ADHD survey could better suit patients.

"I'm excited to be involved in this study, and in efforts to refine our screening tools, especially since few researchers have previously investigated using this scale in children with ASD," added study co author Thomas J. Power, who was a part of the team that developed the ADHD RS IV in the 1990s. "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."

Yerys concluded by saying that while, in a perfect world, clinicians should have experience in diagnosing ADHD and autism, that's not true everywhere.

"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," said Yerys.

The findings, entitled "Evaluation of the ADHD Rating Scale in Youth with Autism", were published in the Journal of Autism and Developmental Disorders and was accompanied by a press release from the Children’s Hospital of Philadelphia.

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