AuDHD Blog
How Common Is Co-Occurring Autism and ADHD?
Co-occurrence is common, but there is no single settled number. Rates change with age, sample type, diagnosis rules, and measurement method.
Research · · 8 min read
The accurate answer is unsatisfying but important: co-occurring autism and ADHD are common, and there is no single settled number that applies to every age, country, clinic, or research method (Hours et al., 2022; Leitner, 2014).
There is no single number
Rates change depending on who is counted. A clinical child sample will not look like a community adult sample. A claims database will not look like a research assessment. A trait questionnaire will not mean the same thing as a formal diagnosis. That is why responsible prevalence writing always names the population and method.
Why older estimates still matter
Rommelse et al. (2010) summarized evidence that approximately 20%-50% of children with ADHD met autism spectrum disorder criteria and approximately 30%-80% of autistic children met ADHD criteria. These ranges are wide and child-focused, but they remain useful because they show co-occurrence was already well recognized in the research literature before AuDHD became common public language.
What real-world records add
Newer service and claims studies add another angle. Zaleski et al. (2025) examined real-world prevalence, cohort characteristics, healthcare use, and expenditures among adults and children with autism, ADHD, or both. Yerys et al. (2025) focused on ADHD in Medicaid-enrolled autistic adults. These sources are useful because they show system-level needs, but records depend on who gets diagnosed, coded, insured, and seen.
A prevalence number is not just a fact about brains. It is also a fact about access, assessment, definitions, and records.
What to do with the uncertainty
The practical takeaway is not panic and not dismissal. Co-occurrence is common enough that autism assessments should consider ADHD, ADHD assessments should consider autism, and support planning should avoid assuming that one diagnosis explains everything (Young et al., 2020).
How to use prevalence numbers
Prevalence numbers are useful when they guide better questions. They become misleading when they are treated as proof that one reader definitely does or does not belong. The safest use is to show that co-occurrence is common enough to deserve routine consideration, while still asking how each person was assessed and supported (Hours et al., 2022; Young et al., 2020).
- For a clinician: "Because autism and ADHD commonly co-occur, can we assess both directly?"
- For a school: "Can support planning consider attention, sensory needs, transitions, and communication together?"
- For yourself: "A statistic cannot diagnose me, but it can justify seeking a fuller assessment."
- For public writing: always name the population, method, age group, and diagnostic definition behind a rate.
What this means for support
The reason prevalence matters is practical. Real-world data show that people with autism, ADHD, or both can differ in healthcare use and support needs, but service records only capture people the system has recognized (Yerys et al., 2025; Zaleski et al., 2025). Public guidance should therefore push toward better assessment access, better service design, and less siloed support.
Use numbers as access arguments
Prevalence numbers are most helpful when they improve access. They can justify asking services to screen both ways, asking schools to coordinate supports, or asking healthcare teams not to treat one diagnosis as the whole explanation. Real-world data are especially useful for service design, even though they depend on who gets recognized by the system (Yerys et al., 2025; Zaleski et al., 2025).
- Use numbers to argue for assessment access, not to diagnose yourself from a percentage.
- Use numbers to challenge siloed services: autism support and ADHD support often need to talk to each other.
- Use numbers to explain why screening both profiles is reasonable when one is already known.
- Use numbers with caveats: sample, age, method, and diagnostic rules matter (Hours et al., 2022).
What a number cannot tell you
A co-occurrence number cannot tell you how much support one person needs, whether a specific person is autistic or has ADHD, or what kind of help will work. It also cannot show who was missed because they masked, lacked access to assessment, did not fit stereotypes, or were never referred. That is why prevalence belongs beside, not above, functional support planning (Hours et al., 2022; Young et al., 2020).
- Use prevalence as a reason to ask broader questions, not as a personal verdict.
- Use functional examples to show need: what fails, where, how often, and what support changes it.
- Remember that service data can show recognized need while still missing people outside the service system (Yerys et al., 2025; Zaleski et al., 2025).
- When sharing a number, pair it with the caveat: sample, age, method, and diagnostic rules matter.
References
- Hours, C., Recasens, C., & Baleyte, J. M. (2022). ASD and ADHD comorbidity: What are we talking about? *Frontiers in Psychiatry, 13*. https://doi.org/10.3389/fpsyt.2022.837424
- Leitner, Y. (2014). The co-occurrence of autism and attention deficit hyperactivity disorder in children: What do we know? *Frontiers in Human Neuroscience, 8*. https://doi.org/10.3389/fnhum.2014.00268
- Rommelse, N. N. J., Franke, B., Geurts, H. M., Hartman, C. A., & Buitelaar, J. K. (2010). Shared heritability of attention-deficit/hyperactivity disorder and autism spectrum disorder. *European Child & Adolescent Psychiatry, 19*(3), 281-295. https://doi.org/10.1007/s00787-010-0092-x
- Yerys, B. E., Tao, S., Shea, L., & Wallace, G. L. (2025). Attention-deficit/hyperactivity disorder in Medicaid-enrolled autistic adults. *JAMA Network Open, 8*(2), e2453402. https://doi.org/10.1001/jamanetworkopen.2024.53402
- Young, S., Hollingdale, J., Absoud, M., Bolton, P., Branney, P., Colley, W., Craze, E., Dave, M., Deeley, Q., Farrag, E., Gudjonsson, G., Hill, P., Liang, H. L., Murphy, C., Mackintosh, P., Murin, M., O'Regan, F., Ougrin, D., Rios, P., ... Woodhouse, E. (2020). Guidance for identification and treatment of individuals with attention deficit/hyperactivity disorder and autism spectrum disorder based upon expert consensus. *BMC Medicine, 18*(1). https://doi.org/10.1186/s12916-020-01585-y
- Zaleski, A. L., Craig, K. J. T., Khan, R., Waber, R., Xin, W., Powers, M., Ramey, U., Verbrugge, D. J., & Fernandez-Turner, D. (2025). Real-world evaluation of prevalence, cohort characteristics, and healthcare utilization and expenditures among adults and children with autism spectrum disorder, attention-deficit hyperactivity disorder, or both. *BMC Health Services Research, 25*(1). https://doi.org/10.1186/s12913-025-13296-2