Autism spectrum disorder (ASD) is frequently comorbid with ADHD. Among adults with ADHD, as many as half are reported to also have ASD.

A Dutch team set out to answer two questions:

1. Do adults with ADHD and comorbid ASD experience less effectiveness of pharmacological treatment for ADHD than adults with only ADHD?
2. Do adults with ADHD and comorbid ASD experience different or more severe side effects of pharmacological treatment for ADHD than adults with only ADHD, as measured in side-effect scores, blood pressure, heart rate, and weight?

This was a retrospective study, using well-documented medical records, of the effects of drug treatment with methylphenidate (MPH), dexamphetamine (DEX), atomoxetine (ATX), bupropion, or modafinil.

The researchers compared 60 adults with comorbid ASD and ADHD to 226 adults with only ADHD. ADHD symptoms were scored using the Conners’ ADHD Rating Scale: Self Report–Short Version (CAARS: S-S). Side effects of ADHD medication were measured using either a 13-item or 20-item checklist with 4-point scales for item response. Researchers also tracked changes in body weight, blood pressure, and heart rate.

Following treatment, ADHD symptoms among the comorbid group declined by a quarter, and among the ADHD-only group by almost a third. There was no significant difference between men and women. Controlling for age, gender, and ADHD subtype, a comorbid diagnosis of ASD also did not significantly affect ADHD symptom reduction.

Turning to side effects, in the ADHD+ASD group, there were significant increases in decreased appetite and weight loss, and decreases in agitation, anxiety, and sadness/unhappiness. In the ADHD-only group, there were significant increases in decreased appetite, weight loss, and dry mouth, and decreases in sleeping disorder, nervousness, agitation, anxiety, and sadness / unhappiness. Yet there were no significant differences between the two groups. Side effects increased and decreased similarly in both. Likewise, there were no significant differences between the groups in changes in heart rate and blood pressure. The only significant difference in medication dosage was for bupropion, which was higher in the ADHD+ASD group, though without any sign of difference in side effects.

The authors concluded that this retrospective study “showed pharmacological treatment of adults with diagnoses of ADHD and ASD to be just as successful as the pharmacological treatment of adults with only ADHD,” but cautioned that “a randomized controlled trial should be conducted to evaluate the effectiveness and possible side effects of pharmacological treatment for ADHD in patients with ASD more reliably.”

REFERENCES
J. J. Muit, N. Bothof, and C. C. Kan, “Pharmacotherapy of ADHD in Adults With Autism Spectrum Disorder: Effectiveness and Side Effects,” Journal of Attention Disorders (2019) DOI: 10.1177/1087054719866255.