In a large study of more than 3.5 million adults, researchers from Children’s Hospital of Philadelphia (CHOP), Drexel University and George Washington University (GWU) found that attention deficit hyperactivity disorder (ADHD) was highly elevated among adults diagnosed with autism spectrum disorder. Additionally, co-occurring ADHD was associated with worse health outcomes, though patients who received medications for ADHD had better outcomes. The findings were published today by the journal JAMA Network Open.
According to the U.S. Centers for Disease Control, there are more than 5 million American adults with autism. Prior studies have shown that adults with autism experience suboptimal health outcomes and early mortality compared with the general population. Anxiety and depression are more common and can lead to lower quality of life. Therefore, many autistic adults and their families are looking for ways to identify health issues and find appropriate interventions.
ADHD is a common co-occurring condition in youth diagnosed with autism and can also lead to poor health outcomes. However, since rates of ADHD often decrease with age, there is a critical knowledge gap about the prevalence of ADHD in adult patients with autism. Understanding its prevalence as well as the effects of managing ADHD with medication could help inform clinical care for these adults.
In this study, researchers conducted an analysis of a cohort of U.S. Medicaid-enrolled adults with autism or intellectual disability. The data was collected between 2008 and 2019 and analyzed between September 2023 and September 2024. The study sample included adults who were at least 18 years old, including autistic adults with and without co-occurring intellectual disability, adults with intellectual disability without autism and adults from a random sample of Medicaid-enrolled individuals. Data from a total of 3,506,661 adults were used in the study.
“Generally speaking, rates of ADHD decrease as children grow up, but we found that ADHD rates among autistic adults were nearly identical to ADHD rates seen in autistic children,” said lead author Benjamin E. Yerys, PhD, a psychologist in the Department of Child and Adolescent Psychiatry and Behavioral Sciences at CHOP and director of the PASSAGE program at the Center for Autism Research. “As rates of autism continue to rise in childhood, at a clinical level, we need to make sure that an increased number of patients with co-occurring ADHD in adulthood have access to support programs that provide autism as well as ADHD services across the lifespan of these patients.”
The study found that compared with the general Medicaid-enrolled population, 27% of autistic adults without intellectual disability had a co-occurring ADHD diagnosis, a 10-fold increase over the general population. Additionally, 40% of adults with autism with intellectual disability and 19% of adults with intellectual disability but no autism had co-occurring ADHD. Fewer than 50% of all adults with ADHD received any ADHD-medication prescription.
For adults with an ADHD diagnosis, rates of substance use, cardiovascular conditions and rates of injury were also higher compared to adults without ADHD. However, adults with ADHD who received ADHD medications had lower rates of substance use, cardiovascular conditions, and injury with one exception. ADHD medications were not associated with lower substance use rates among autistic adults with intellectual disability and ADHD diagnosis compared to those adults not taking ADHD medications.
Using these findings as a starting point, the study authors suggest that there is an opportunity to better coordinate services across behavioral health, physical health and developmental disabilities services for these patients, and identifying which issues – like substance abuse – are more prevalent and can lead to more targeted interventions during routine care appointments.
