The comorbidity of ADHD and autism spectrum disorder

Abstract

ADHD and autism spectrum disorder are common psychiatric comorbidities to each another. In addition, there is behavioral, biological and neuropsychological overlap between the two disorders. There are also several important differences between autism spectrum disorder and ADHD. Treatment strategies for the comorbid condition will also be reviewed. Future areas of research and clinical need will be discussed.

Keywords::

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

Financial & competing interests disclosure

In the past year, SV Faraone has received consulting income and/or research support from Akili Interactive Labs, VAYA Pharma and SynapDx, and research support from the National Institutes of Health. SV Faraone's institution is seeking a patent for the use of sodium-hydrogen exchange inhibitors in the treatment of ADHD. In previous years, SV Farone has received consulting fees or was on Advisory Boards or participated in continuing medical education programs sponsored by Shire, Alcobra, Otsuka, McNeil, Janssen, Novartis, Pfizer and Eli Lilly. SV Faraone receives royalties from books published by Guilford Press (Straight Talk about Your Child's Mental Health) and Oxford University Press (Schizophrenia: The Facts). 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.

No writing assistance was utilized in the production of this manuscript.

Key issues

• • In the DSM-IV-TR, ADHD Criterion E prohibits clinicians from making an ADHD diagnosis in the context of autism spectrum disorder (ASD). In the DSM-5, this exclusionary criterion has been removed and clinicians are now able to make an ADHD diagnosis in the context of ASD.

• • A majority of children with ASD (31–95%) have significant symptoms of inattention and/or hyperactivity/impulsivity, not all children with ASD have these symptoms.

• • ADHD-Inattentive type is somewhat more common in ASD than ADHD-Combined type.

• • ASD and ADHD are both associated with impaired social interaction, yet data suggest that the social interaction impairments are more significant in ASD.

• • Genetic linkage studies suggested regions of chromosomes 16p13, 2q24, 16p1, 17p11, 5p13 and 15q to be involved in both ADHD and ASD.

• • Genes in dopaminergic, serotoninergic, glutamatergic and and GABAergic systems have been implicated in both disorders.

• • ADHD and ASD are thought to be associated with (or defined by) executive dysfunction although the specific executive domains that are negatively impacted may differ. Children with ASD have more planning and cognitive flexibility difficulties and children with ADHD have more inhibition difficulties.

• • Atomoxetine and methylphenidate both show evidence for treating ADHD symptoms within individuals with ASD. However, effect sizes from the ASD population are somewhat smaller than the non-ASD population and side effects are more common in the ASD population.