A new study reveals that attention deficit hyperactivity disorder (ADHD) continues to affect adults with autism at rates similar to those seen in childhood, challenging the common understanding that ADHD symptoms typically diminish with age.
Researchers from the Children's Hospital of Philadelphia found that approximately 27% of adults with autism but no intellectual disabilities also had an ADHD diagnosis—a rate ten times higher than the general population. This figure rises to 40% among autistic adults who also have intellectual disabilities.
"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," explained study lead author Benjamin Yerys, a psychologist at the Children's Hospital of Philadelphia and director of the PASSAGE program at the hospital's Center for Autism Research.
The findings, published February 12 in JAMA Network Open, analyzed Medicaid data from 2008 to 2019 covering more than 3.5 million U.S. adults.
Health Implications of Dual Diagnosis
The research team discovered that adults with both autism and ADHD experienced significantly poorer health outcomes compared to those with autism alone. These individuals showed markedly higher rates of substance use disorders, cardiovascular conditions, and injuries.
Notably, the study found that fewer than half of adults with both conditions received any form of medication for their ADHD. However, when patients did receive appropriate ADHD treatment, many of the associated physical health complications were substantially reduced.
"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," Yerys emphasized.
Rising ADHD Diagnoses Among Adults
This research emerges against a backdrop of increasing ADHD diagnoses in the adult population overall. A separate study published in January 2025 in Psychiatric Research and Clinical Practice reported a 15% increase in adult ADHD diagnoses between 2020 and 2023, following an 11% decline from 2016 to 2020.
Dr. Erick Messias, chair of psychiatry and behavioral neurosciences at St. Louis University School of Medicine, who led this research, attributed the rise to "a complex interplay of various factors," including greater awareness, reduced stigma, improved access to healthcare services, and expanded diagnostic guidelines.
Adult ADHD can present differently than childhood manifestations, with symptoms including chronic forgetfulness, procrastination, restlessness, lack of follow-through, and frequently misplacing items—making it potentially more challenging to identify.
Clinical Implications
The persistence of ADHD into adulthood for individuals with autism highlights the need for continued support and treatment options throughout the lifespan. The substantial reduction in negative health outcomes observed when ADHD is properly treated suggests that improving diagnosis and treatment rates could significantly benefit this population.
Healthcare providers should be aware that unlike in the general population, where ADHD symptoms often diminish with age, individuals with autism may require ongoing assessment and management of ADHD symptoms well into adulthood.
The findings underscore the importance of developing specialized support programs that address both conditions simultaneously and ensuring that adults with autism have access to comprehensive mental health services that recognize and treat co-occurring conditions like ADHD.
