Key finding
Published estimates of ADHD among autistic children and adults range from 26% to 70% across four of the seven peer-reviewed studies (2008–2022) summarized on this page. Pooled meta-analysis estimates sit near 28%. In the other direction, the remaining three studies place autism among people with ADHD at 12% to 24%.
Source: seven PubMed-indexed studies, verified 19 August 2026.
What the studies report
The table lists seven peer-reviewed publications: three meta-analyses, two large registry or survey studies, one population-derived cohort, and one narrative review. Each estimate is taken from the study’s own published abstract. Click a study name to open its PubMed record.
| Study | Year | Population | N | Reported overlap estimate |
|---|---|---|---|---|
| Lai et al., Lancet Psychiatry | 2019 | Autistic people (all ages) — meta-analysis of 96 studies with clinical DSM/ICD diagnoses | 96 studies | Pooled ADHD prevalence 28% (95% CI 25–32) |
| Simonoff et al., J Am Acad Child Adolesc Psychiatry | 2008 | Autistic children aged 10–14, UK population-derived cohort | 112 | ADHD in 28.2% (95% CI 13.3–43.0) |
| Mutluer et al., Front Psychiatry | 2022 | Autistic children and adolescents — meta-analysis of 39 population-based studies | 39 studies | ADHD prevalence 26.2% (95% CI 22–31) |
| Hours et al., Front Psychiatry | 2022 | People with autism — narrative review of the clinical literature | Review | Reports a literature range of 50–70% with co-occurring ADHD |
| Hollingdale et al., Psychol Med | 2020 | Children and adolescents with ADHD — meta-analysis of 22 studies | 61,985 | 21% met the threshold for autism (community samples 19%, clinical samples 24%) |
| Jensen & Steinhausen, Atten Defic Hyperact Disord | 2015 | Children and adolescents (age 4–17) with ADHD, Danish psychiatric hospitals 1995–2010 | 14,825 | Autism spectrum disorder diagnosed in 12.4% |
| Zablotsky et al., J Atten Disord | 2020 | US children with a current ADHD diagnosis, 2014 national survey | 2,464 | About one in eight also diagnosed with autism |
Reading the spread
There is no single agreed number. Estimates of ADHD among autistic people range from 26% to 70%, depending on who was studied and how. The two large meta-analyses land close together: 28% pooled across 96 studies (Lai et al., 2019) and 26.2% across 39 population-based studies of children and adolescents (Mutluer et al., 2022). The higher figures of 50–70% come from a narrative review of the clinical literature (Hours et al., 2022), not from a pooled analysis.
The reverse direction runs lower. Among children and adolescents diagnosed with ADHD, a meta-analysis of 22 studies found 21% met the threshold for autism (Hollingdale et al., 2020). A Danish nationwide hospital study found autism diagnosed in 12.4% of 14,825 young ADHD patients (Jensen & Steinhausen, 2015), and a US national survey found about one in eight children with ADHD also had an autism diagnosis (Zablotsky et al., 2020). The asymmetry makes sense: ADHD is the more common diagnosis, so the overlap group is a bigger share of the smaller autistic population.
Why the estimates differ so much
- Diagnostic rules changed. DSM-IV did not allow autism and ADHD to be diagnosed in the same person. DSM-5 (2013) allows both. Studies that recruited before that change may undercount the overlap; studies using research assessments were less affected.
- Clinical vs community samples. People seen in clinics tend to have more co-occurring conditions and more severe symptoms than people found through population sampling. Lai et al. (2019) reported higher estimates in clinical samples than in population and registry studies, and Hollingdale et al. (2020) found 24% in clinical samples against 19% in community samples, though that difference was not statistically significant.
- Symptoms vs formal diagnosis. Studies that count people who meet a symptom threshold on a questionnaire report higher numbers than studies that count confirmed clinical diagnoses.
- Age of the sample. Most of the large studies are in children and adolescents. Adult-specific estimates are scarcer, and diagnostic practice for adults has shifted a lot in the past decade.
Takeaway
Roughly a quarter of autistic people also meet criteria for ADHD in pooled analyses, and some clinical literature reports much higher rates. Roughly one in eight to one in five young people with ADHD also meet criteria for autism. All of these figures are group averages from specific samples. None of them says anything certain about any one person, and the true adult rates are less well measured than the child rates. If both profiles feel familiar, that is a reason to discuss both with a clinician — not a probability you can compute from this table.
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Full citations, each linked to its PubMed record. Retrieved via PubMed, 19 August 2026.
- Lai MC, Kassee C, Besney R, et al. Prevalence of co-occurring mental health diagnoses in the autism population: a systematic review and meta-analysis. Lancet Psychiatry. 2019;6(10):819–829. PMID 31447415
- Simonoff E, Pickles A, Charman T, Chandler S, Loucas T, Baird G. Psychiatric disorders in children with autism spectrum disorders: prevalence, comorbidity, and associated factors in a population-derived sample. J Am Acad Child Adolesc Psychiatry. 2008;47(8):921–929. PMID 18645422
- Mutluer T, Aslan Genç H, Özcan Morey A, et al. Population-based psychiatric comorbidity in children and adolescents with autism spectrum disorder: a meta-analysis. Front Psychiatry. 2022;13:856208. PMID 35693977
- Hours C, Recasens C, Baleyte JM. ASD and ADHD comorbidity: what are we talking about? Front Psychiatry. 2022;13:837424. PMID 35295773
- Hollingdale J, Woodhouse E, Young S, Fridman A, Mandy W. Autistic spectrum disorder symptoms in children and adolescents with attention-deficit/hyperactivity disorder: a meta-analytical review. Psychol Med. 2020;50(13):2240–2253. PMID 31530292
- Jensen CM, Steinhausen HC. Comorbid mental disorders in children and adolescents with attention-deficit/hyperactivity disorder in a large nationwide study. Atten Defic Hyperact Disord. 2015;7(1):27–38. PMID 24942707
- Zablotsky B, Bramlett MD, Blumberg SJ. The co-occurrence of autism spectrum disorder in children with ADHD. J Atten Disord. 2020;24(1):94–103. PMID 28614965