An update on the comorbidity of ADHD and ASD: a focus on clinical management

ABSTRACT

Attention deficit/hyperactivity disorder (ADHD) and autism spectrum disorder (ASD) commonly co-occur. With the DSM-5, clinicians are permitted to make an ASD diagnosis in the context of ADHD. In earlier versions of the DSM, this was not acceptable. Both ASD and ADHD are reported to have had substantial increases in prevalence within the past 10 years. As a function of both the increased prevalence of both disorders as well as the ability to make an ASD diagnosis in ADHD, there has been a significant amount of research focusing on the comorbidity between ADHD and ASD in the past few years. Here, we provide an update on the biological, cognitive and behavioral overlap/distinctiveness between the two neurodevelopmental disorders with a focus on data published in the last four years. Treatment strategies for the comorbid condition as well as future areas of research and clinical need are discussed.

KEYWORDS:

• ADHD
• autism spectrum disorder
• ASD
• neurodevelopmental disorder
• developmental delay
• comorbidity
• children
• adolescent

Financial & competing interests disclosure

S. Faraone received income, potential income, travel expenses and/or research support from Pfizer, Ironshore, Shire, Akili Interactive Labs, CogCubed, Alcobra, VAYA Pharma, Neurovance, Impax and NeuroLifeSciences. With his institution he has US patent US20130217707 A1 for the use of sodium-hydrogen exchange inhibitors in the treatment of ADHD. In previous years, he has received income or research support from Shire, Alcobra, Otsuka, McNeil, Janssen, Novartis, Pfizer and Eli Lilly. S. Faraone receives royalties from books published by Guilford Press: Straight Talk about Your Child’s Mental Health, Oxford University Press: Schizophrenia: The Facts and Elsevier: ADHD: Non-Pharmacologic Interventions. The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed.

Key issues

• In the DSM-5, ADHD is now permitted to be diagnosed in an individual with ASD. Prior to the DSM-5, this practice was not sanctioned.

• The majority of individuals with ASD have ADHD symptoms. A substantial minority of individuals with ADHD (15–25%) demonstrates ASD symptoms.

• Executive functioning impairments are associated with both ADHD and ASD and much of the recent cognitive research on the comorbid state has focused on executive functioning.

• Brain structure studies of ADHD and ASD have found both shared and distinct neural features in gray and white matter structures.

• ASD + ADHD is associated with more severe impairments in adaptive behavior when compared to children with ASD alone.

• Compared to children and adolescents, far less recent research has considered ADHD in adults with ASD.

• Methylphenidate and atomoxetine have been researched the most in ASD + ADHD. Both have demonstrated efficacy although with lower effect sizes and increase side effects relative to what is reported in ADHD (without ASD).

• Despite knowing much about what is an effective nonpharmacological intervention for ADHD and ASD in isolation, we presently know very little about what constitutes effective nonpharmacological interventions for the comorbid state.