Interest in the co-occurrence of autism spectrum disorder (ASD) and attention-deficit/hyperactivity disorder (ADHD) has grown in the last decade. Both are neurodevelopmental disorders with onset of symptoms in early childhood. Research, practice and theoretical models indicate that these disorders frequently overlap and co-occur. For example, studies conducted in the US and Europe indicate that children with ASD in clinical settings present with comorbid (co-occurring) symptoms of ADHD with rates ranging between 37% and 85%. More severe externalizing, internalizing and social problems, as well as more impaired adaptive functioning, and more autistic traits and maladaptive behaviors have been reported in children with both ASD and ADHD than children identified with only ASD. For example, researchers found that early school-age children with co-occurrence of ASD and ADHD were significantly more impaired than children with only ASD on measures of cognitive and social functioning, as well as in the ability to function in everyday situations. They were also more likely to have significant cognitive delays and display more severe autism mannerisms, such as stereotypic and repetitive behaviors in comparison with children identified with only ASD.
It is imperative that practitioners recognize the high co-occurrence rates of these two disorders as well as the potential increased risk for social and adaptive impairment associated with comorbidity of ASD and ADHD. Children with the combined presence of ADHD and ASD may need different treatment methods or intensities than those with ASD only in order to achieve better outcomes.
If clinically significant ADHD symptoms are identified, and social development does not appear to be responding to intervention, changes in the intervention program (e.g. intensity, strategies, and goals) may be required. It is also important to note that a significant change in the DSM-5 is removal of the DSM-IV-TR hierarchical rules prohibiting the concurrent diagnosis of ASD and ADHD. When the criteria are met for both disorders, both diagnoses are given. Thus, an assessment of ADHD characteristics should be included whenever inattention and/or impulsivity are indicated as presenting problems. More research is needed to further clarify the behavioral characteristics of children with co-occurring ASD and ADHD so that specialized treatments and interventions may be designed to improve outcomes and quality of life for this group of children.
Rao, P. A., & and Landa, R. J. (2014). Association between severity of behavioral phenotype and comorbid attention deficit hyperactivity symptoms in children with autism spectrum disorders. Autism, 18, 272-280.
Lee A. Wilkinson, PhD, NCSP, CPsychol, AFBPsS is author of the award-winning book, A Best Practice Guide to Assessment and Intervention for Autism and Asperger Syndrome in Schools, published by Jessica Kingsley Publishers. He is also editor of a recent volume in the American Psychological Association (APA) School Psychology Book Series, Autism Spectrum Disorder in Children and Adolescents: Evidence-Based Assessment and Intervention in Schools and author of the new book, Overcoming Anxiety and Depression on the Autism Spectrum: A Self-Help Guide Using CBT.