Autism and ADHD together

ADHD is one of the conditions most often found alongside autism. A 2019 meta-analysis of studies that used confirmed clinical diagnoses put ADHD in 28% of autistic people, with wide variation between studies.¹ A 2021 meta-analysis of 63 studies found ADHD at the time of the study in 38.5% of autistic people, and at some point in life in 40.2%.² Counting only population-based studies of autistic children and adolescents, the figure was 26.2%.³

The overlap runs the other way too. Pooling 22 studies of children and adolescents with ADHD, about 21% met the threshold for autism, with no clear difference between community samples (19%) and clinical ones (24%). Young people with ADHD also scored much higher on measures of autistic traits than those without.⁴ Among children and adolescents treated for ADHD in Danish psychiatric hospitals between 1995 and 2010, 12.4% of 14,825 had an autism diagnosis at the same time.⁵ Among 1.9 million people born in Sweden, autistic people had about 22 times the odds of an ADHD diagnosis, and the link was stronger in autistic people without an intellectual disability.⁶

Under DSM-IV and its 2000 revision, the American manual used by most researchers, autism and ADHD could not be diagnosed in the same person.^7,8 Researchers were reporting ADHD traits in autistic children before the rule changed.^9,10 DSM-5, published in 2013, was the first edition to recognize the two formally as co-occurring conditions.⁸ Clinical guidance on people with both is therefore recent; a UK expert group published one of the first consensus statements in 2020.⁸

A 2019 narrative review concluded that the two share features, such as differences in social functioning and in executive function, but differ enough to remain separate diagnoses.¹¹

Many people with both diagnoses call themselves "AuDHD". The term comes from autistic and ADHD communities, not from the diagnostic manuals, and some researchers have started to use it for children with both diagnoses.¹³

Twin studies compare identical twins, who share all their genes, with non-identical twins, who share about half. In a community sample of 8-year-old twins in England and Wales, autistic and ADHD traits rated by parents and teachers went together (correlations of about 0.5). Much of the genetic influence on one also influenced the other, including at the extreme end of the traits.⁹

In a Swedish study of about 11,000 twin pairs screened by parent telephone interview, genes accounted for about 80% of the variation in likelihood of autism (with a wide margin of uncertainty) and 79% for ADHD. Among identical co-twins of autistic children, 44% met criteria for ADHD, against 15% of non-identical co-twins.¹⁴ Swedish national registers, which record clinical diagnoses, show the same pattern: the link between one relative's autism and another's ADHD was strongest between identical twins (odds ratio 17.8), and weaker between non-identical twins (4.3) and full siblings (4.6).⁶ A 2010 review of family and twin studies concluded that autism and ADHD arise partly from the same familial and genetic factors.¹⁵

Studies that scan the whole genome find a moderate overlap between the common genetic variants linked to autism and those linked to ADHD. The genetic correlation was 0.36 in a large 2019 autism study and 0.42 in a 2023 ADHD study.^16,17 In the 2023 study, a model estimated that about three-quarters of the variants influencing both conditions pushed in the same direction, though the authors say this model had only limited support for autism.¹⁷

The overlap is partial and does not all run the same way. The 2019 autism study found a positive genetic correlation with years of education (about 0.20), while the 2023 ADHD study found a negative one (about -0.55).^16,17 The twin study from England and Wales, which measured overlap a different way, found genetic correlations above 0.5.⁹

Rare variants show a similar picture. In about 8,000 children with autism, ADHD or both, and 5,000 without, autistic and ADHD children carried a similar excess of rare variants that disrupt genes, both above the comparison group.¹⁸

Where the overlap sits may depend on when the autism is diagnosed. A 2025 study split the autism polygenic signal into two modestly correlated factors (about 0.38). One went with an autism diagnosis in early childhood and lower social and communication abilities at that age; the other went with a later diagnosis and more socioemotional and behavioral difficulties in adolescence. The later-diagnosis factor had a moderate-to-high genetic correlation with ADHD (about 0.5 to 0.7), and the earlier-diagnosis factor's correlation with ADHD was low (about 0.1 to 0.2).³¹ In the same study, the genetic correlation between autism and ADHD rose the later the autism was diagnosed, which the authors use to explain why earlier autism studies found a weaker link with ADHD than newer ones. The same later-diagnosis factor was also genetically correlated with depression, PTSD, childhood maltreatment and self-harm, and the authors found that these links were not fully explained by its link to ADHD.³¹

In a US national survey, parents of 1,496 autistic children reported when each diagnosis was made. About 20% of the children had been diagnosed with ADHD first. They received their autism diagnosis about 3 years later than autistic children whose ADHD was diagnosed at the same time or afterwards, and in this survey had nearly 30 times the odds of being diagnosed autistic after age 6.¹⁹

A study using the Netherlands Autism Register found the same in children and adolescents: those with an earlier ADHD diagnosis were diagnosed autistic 1.8 years later on average. Within this one register, the delay was 1.5 years in boys and 2.6 years in girls, a subgroup result that has not been repeated. No clear delay was found in adults, but few of them had an earlier ADHD diagnosis and the authors urge caution.²⁰ The authors suggest that overlapping traits may lead to ADHD being diagnosed instead of autism, or make autism harder to notice once ADHD has been diagnosed.²⁰

In the same register, 24.6% of 1,211 autistic adults, mostly well educated, reported an earlier psychiatric diagnosis they now saw as a misdiagnosis. ADHD was among the diagnoses named, after personality, anxiety, mood and burnout-related ones.²¹

Assessment tools built for autism do not always separate the two. In autism clinics, among 48 school-age children whose final diagnosis was ADHD, 21% scored above the autism cut-off on the ADOS, an observation-based assessment, and 30% on all areas of the ADI-R, a parent interview. Four ADOS items on social communication told the groups apart; no ADI-R item did.²²

Thinking skills overlap as well. A meta-analysis of 58 studies that tested autistic and ADHD children side by side found no significant differences in their executive function, which does not show that the two profiles are the same.²³ A larger meta-analysis of 180 studies found executive-function differences across all the conditions it covered, with few differences between them, though autistic children had more difficulty switching between tasks than ADHD children.²⁴

Autistic children with clinically significant ADHD symptoms on parent ratings had lower scores for everyday skills and for parent-rated quality of life than autistic children with fewer ADHD symptoms.²⁵ A study of autistic children aged 4 to 8 found that those with ADHD symptoms had lower cognitive scores, more marked social difficulties and greater delays in everyday skills.⁷ A small study of children matched on age, sex and IQ found poorer executive control, adaptive behavior and verbal working memory in autistic children with ADHD symptoms.¹⁰ Not every area differs: among 282 children with autism, ADHD or both, social difficulties did not differ between autism alone and autism with ADHD.²⁶

In adults, 724 autistic people who joined a US online research registry and rated themselves as having more ADHD symptoms also reported less independence in daily living and lower quality of life.²⁷ In a Swedish study of 314 twins aged 8 to 21, having more neurodevelopmental conditions of any kind, not only autism and ADHD, went with more difficulty in everyday functioning, as rated by parents.²⁸ Across 180 studies of children, executive-function differences were larger when children had more than one condition.²⁴

Evidence on self-harm and suicide is limited and correlational. A review found only three studies on self-harm, each reporting somewhat higher odds in autistic people with ADHD than in those without (odds ratios from 1.07 to 1.65); the reviewers urge caution because so few studies exist.²⁹ In Swedish national registers covering about 54,000 autistic people, suicide attempts and suicide were most common in autistic people without an intellectual disability who also had ADHD, with odds about 7 times and 13 times those of matched people without autism. This held in both women and men, and the figures shrank when other psychiatric conditions were taken into account.³⁰

Many people with both diagnoses use "AuDHD" as a name for a shared experience and a community, not only as two labels. Megan Griffith wrote Welcome to AuDHD for adults like herself and puts it plainly: "Being AuDHD is incredibly different from being solely autistic or being solely ADHD."^c1 She describes the two as playing off, hiding and worsening each other. A special interest can cover for daydreaming in class, and ADHD's sense of time as "now" or "not now" can make a meltdown the night before feel long past by morning.^c1 Griffith also writes that "our community has been far ahead of the medical community on the common co-occurrence of autism and ADHD", and that many people diagnosed with one condition as children learned they were AuDHD from social media.^c2 That is a description of lived experience. The research above finds the evidence on whether people with both differ from autistic people without ADHD to be mixed.

Sara Woods, a clinical psychologist writing for the Thinking Person's Guide to Autism in 2026, gives the same view a name. Autism and ADHD traits, she writes, "overlap, intersect, and interact" in the way red and blue mix in a tie-dye shirt, so "each person's neurotype is a little different even if they could all be described as AuDHD."^c11 She describes AuDHD as its own experience rather than autism plus ADHD, notes that the term took off online around 2022, and treats the accounts of AuDHDers themselves as central to the case for the label.^c11

Griffith and Megan Anna Neff, who also calls herself an "AuDHDer", both describe a narrow band of comfortable stimulation.^c1,c5 Griffith calls it a narrow window of tolerance, in which "we are both easily overstimulated and easily understimulated"; she links the first mostly to autistic sensory sensitivity and the second mostly to the ADHD need for stimulation.^c1 Neff calls the right amount the "Goldilocks zone".^c5

Devon Price, who is autistic without ADHD, calls the two "sibling disabilities, two highly similar groups who belong in community with one another".^c4 Price writes that people with ADHD are usually treated as honorary members of the autistic self-advocacy community. Price also describes where needs can clash: Price needs a quiet, clean space by day and darkness to sleep, while many ADHD friends need noise, novelty and sensory input.^c4

Pete Wharmby, an autistic writer who was two years into a wait for an ADHD diagnosis when writing Untypical, calls the links between the two conditions well known but "absolutely bewildering".^c6 Wharmby puts a mind that "simply never shuts up" down mostly to ADHD, and the endless noticing of number plates and patterns that fills it down to autism. Aimed at a special interest, the same chatter turns into something like the narrator of a fascinating documentary; the rest of the time it is "grating and exhausting".^c6

Griffith treats AuDHD as part of who she is: "AuDHD is an integral part of who I am."^c3 She also writes that she does not love every part of it. She names a family party where overstimulation led to a verbal shutdown, and the daily effect of ADHD on her executive functioning; for her, accepting herself and disliking some traits sit side by side.^c3

Writers on diagnosis describe one label standing in for the other. Daniel Burford, who writes for adults diagnosed late, notes that until 2013 the diagnostic manual made clinicians choose: "Most of them wrote ADHD, because ADHD was the one they'd been taught to see in a clinic full of adults."^c7 Jules Edwards, writing as a parent, describes a clinic that diagnosed one of their sons with oppositional defiant disorder, ADHD and an unspecified neurodevelopmental disorder and at first refused to assess him for autism, which an autism specialist later confirmed.^c8 Indigo, one of the autistic adults whose accounts Alex Ratcliffe collected, was diagnosed at 51 as autistic "with executive functioning issues (ADHD)".^c9 The clinicians Donna Henderson, Sarah Wayland and Jamell White, in a guide to diagnosis, warn against the opposite mistake. They argue that "many people, including clinicians, overestimate the overlap between the two", so that autistic traits get put down to ADHD.^c10 They also list differences, among them that some people with ADHD seek novelty, which they do not expect in most autistic people, who tend to need sameness.^c10