Scientists are starting to understand how autism and ADHD can overlap

Colleen Cira first recognized her own attention deficit hyperactivity disorder (ADHD) while having her children assessed—an experience clinicians say is increasingly common among adults whose symptoms went unnoticed earlier in life.

“I was like, ‘This is me too.’ I'm constantly double-booking appointments. I'm always late. I interrupt people a lot. I can be quite impulsive,” says the clinical psychologist and founder of the Cira Center for Behavioral Health, who was diagnosed aged 35. But it took another seven years before Cira and her two children were also diagnosed with autism spectrum disorder, which is characterized by differences in social interaction and sensory sensitivities.

These neurodevelopmental conditions “overlap, but they are opposite in many ways, so there is this experience of just feeling constantly at war with yourself,” says Cira, who uses a wine analogy to describe her particular blend of ‘AuDHD’. “I'm ADHD forward—that's the first thing you're going to see about me—with an autism finish.”

That overlap—often referred to as AuDHD in autism and ADHD communities —is not an official diagnosis. But it’s gaining attention as research suggests the co-occurrence of ADHD and autism may be both common and widely underrecognized. A 2025 study estimated that roughly 45 percent of adults with ADHD show significant autistic traits. Yet an analysis of 1.9 million U.S. insurance claims from the same year found that only 1.7 percent of adults with ADHD had a co-existing ASD diagnosis.

The gap points to a growing realization among researchers: when ADHD and autism occur together, they can obscure each other—making both harder to recognize and diagnose. Scientists are now working to understand how this overlap shapes symptoms, why it’s so often missed, and what it means for the people living with it.

What is AuDHD?

Until 2013, clinicians weren’t allowed to diagnose a person with both ADHD and autism. The fifth edition of the Diagnostic and Statistical Manual of Mental Disorders changed that, acknowledging that ADHD and autism can co-exist and share certain features, particularly in terms of attention.

“Someone with autism might have special interests and focus on those,” says clinical psychologist Natasha Langan. “Someone with ADHD may have difficulties regulating and sustaining their attention, but they can also have specialist interests so they can hyperfocus at times.”

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At the same time, other traits can pull in different directions. A preference for routine—common in autism—may conflict with the novelty-seeking and impulsivity associated with ADHD. For some, that creates an internal tension between structure and change, says Langan. 

AuDHD presentation “varies tremendously because autistic individuals and ADHD individuals vary tremendously,” says Kelly Carrasco, psychologist and assistant professor at California State University, Fresno. Researchers are still trying to determine why the two disorders often co-exist. Both conditions are highly heritable, and growing evidence suggests they are partly rooted in shared biology—not entirely separate disorders.

A large 2022 genomic study found that ADHD and autism share multiple regions of genetic risk, including at least seven loci linked to both conditions, alongside others that differentiate them. Twin and family studies suggest a strong shared genetic signal between ADHD and autism, with some estimates indicating that much of the risk for one condition overlaps with the other. 

More recent work is beginning to map how those shared genes translate into the brain. A 2025 neuroimaging study found that people with co-occurring ADHD and autism show distinct patterns of brain structure and connectivity—suggesting the combination is not just additive, but may represent a unique neurodevelopmental profile. Taken together, the findings point to what researchers describe as a “complex interplay of genetic, biological, and phenotypic factors” involved in AuDHD.

How common is it?

Determining the true prevalence of AuDHD is difficult.  Part of the challenge is how co-occurrence is measured. Some studies look at shared traits, while others count only formal dual diagnoses—and the results can look dramatically different. A 2023 review found ADHD symptom prevalence varied from 2.6 percent to 95.5 percent in children and adolescents with autism spectrum disorder, while a 2025 longitudinal study of 165 adults with ADHD found that 44.8 percent showed traits of autism.

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However, analysis of 1.9 million health insurance claims from the United States in 2025 found just 1.7 percent of adults with ADHD had a co-existing diagnosis of autism, which the researchers say “may signal potential underdiagnosis and warrants additional exploration”. The discrepancy may be explained by the number of people who have one diagnosis and show some traits of the other condition, but not enough to meet the diagnostic threshold.  

“There are justifiable critiques of this categorical system where you either have the condition or you don't,” Carrasco says. She also believes that, given the relatively recent 2013 change to the DSM, healthcare providers haven’t yet caught up with AuDHD assessment protocols. “Many clinicians are trained to try and understand what the primary concern is, so they may not see a necessity for an additional diagnostic label.”

Given that autism and ADHD are both known to be underdiagnosed, it can be hard to spot the signs of either, particularly if masking of symptoms occurs. “Particularly women and girls, why they get missed and misdiagnosed is because they can be better at masking or knowing what's the ‘right’ way to behave and act,” Langan says. “What you can find is people coming through mental health services with diagnoses of mood difficulties, depression, anxiety, and that might be a result of living with undiagnosed neurodivergence.”

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In addition, symptoms of one condition can overshadow the other, Cira says. “People who have both, they often wait the longest to get diagnosed because the autism masks some of the ADHD and the ADHD changes some of the autism.” As such, one condition might become more evident when the other subsides, Langan says. “If you treat the ADHD, someone might be calmer, and then you might see more of the autism traits starting to come through.”

How is AuDHD treated?

There’s no single treatment for AuDHD. Instead, care typically involves adapting existing approaches for ADHD and autism to reflect how the two conditions interact.

That matters, experts say, because co-occurring ADHD and autism are often linked to more complex health needs. The 2025 health insurance study found higher healthcare use and costs among people with both conditions, along with increased odds of additional health challenges. “When people have both conditions, it leads to more impairment in different areas of life, like work and relationships,” says Langan.

(How to determine if you’re at risk for adult ADHD.)

Treatment can also be less straightforward. Medication commonly prescribed for ADHD—particularly stimulants—can improve focus and attention, but may not be well tolerated by everyone with autism, Carrasco says. “There are some known side effects that can make stimulant medication intolerable for people, like appetite suppression and feelings of nausea, and there are some reports that we're seeing higher rates of that in this combined population.”

Because of this, clinicians often take a more individualized approach, combining medication, behavioral therapy, and environmental supports tailored to the person’s specific mix of traits. 

But experts say one of the biggest barriers isn’t treatment—it’s recognition.

Without an accurate diagnosis, people may spend years navigating challenges without understanding their underlying cause. “The worst part is individuals having to live with shame or guilt for so many years thinking, ‘Why is it that everybody else seems to have it together?’ or ‘Other people think I'm lazy or unmotivated,’” Carrasco says.

Getting an appropriate diagnosis can help people “separate themselves from that and say, ‘This is how my brain works. This is not an inherent fault in me. This is just how I function, and that's OK.’”