Autism and ADHD: when they overlap (AuDHD)

Until 2013, a clinician diagnosing a child with autism couldn't also diagnose ADHD. The two conditions were treated as mutually exclusive in the diagnostic manual. This has since changed — and it has opened up a much more accurate picture of what's happening for a significant number of neurodivergent children and adults.

The term AuDHD has emerged from the community to describe the lived experience of having both conditions. It's not a formal diagnosis; it's a useful shorthand for a real and common presentation.

How common is the autism-ADHD overlap?

Research puts the co-occurrence rate somewhere between 30% and 50% of autistic individuals also meeting criteria for ADHD, depending on the study. Around 28% of autistic children meet formal ADHD criteria in clinical samples. Estimates going the other way — how many people with ADHD are also autistic — are lower but also significant.

The genetic overlap between the two conditions is substantial, with studies suggesting roughly 50–72% genetic overlap, meaning the same genes are contributing to both. This isn't just comorbidity in the sense of two separate things happening at once; the conditions share neurobiological mechanisms, particularly around executive function, attention regulation, and sensory processing.

Key numbers:

• 30–50% of autistic individuals may have co-occurring ADHD
• 28% of autistic children meet formal ADHD criteria in clinical studies
• Co-occurring AuDHD is associated with significantly higher rates of anxiety, emotional dysregulation, and other mental health challenges than either condition alone

How autism and ADHD are different — and where they look the same

Understanding the overlap matters because the conditions interact, and the interaction can make both harder to see.

AutismBoth — AuDHDADHD

Both — AuDHD — characteristics

• Executive function difficulties (starting, planning, organising)
• Emotional dysregulation — often amplified beyond either alone
• Hyperfocus on areas of interest
• Sensory sensitivities
• Social difficulties and misreading cues
• Sleep problems
• High rates of anxiety and other mental health challenges

28–50% of autistic people also have ADHD. The overlap zone often shows amplified difficulties compared to either condition alone.

For a child or adult with both, these can produce an internal contradiction: the autistic need for routine pulling against the ADHD drive toward novelty; the hyperfocus of autism combining with the distractibility of ADHD in ways that are highly context-dependent. Clinicians and researchers describe AuDHD individuals as sometimes experiencing a heightened version of the shared characteristics and an internal struggle between the contrasting ones.

Why AuDHD gets missed

Before 2013 it couldn't be diagnosed. That's one reason. But there are others.

If a child is seen first through an autism lens, their attention and hyperactivity difficulties may be attributed to autism and not investigated further. If they're seen first through an ADHD lens, their social communication differences and sensory needs may be attributed to ADHD without anyone looking deeper. Either way, the full picture doesn't emerge.

Girls are particularly likely to be missed, as both autism and ADHD in girls are underdiagnosed for overlapping reasons. See the autism in girls guide and the ADHD hub for more on this.

The practical consequence of an incomplete diagnosis is that support is incomplete too. Strategies that work for ADHD without accounting for autism, or vice versa, will only go so far.

Do I have autism, ADHD, or both?

This is one of the most searched questions about autism and ADHD — and it's worth answering carefully, because the distinction isn't always clean.

Both conditions involve executive function difficulties, sensory sensitivities, emotional dysregulation, and social challenges. The traits that feel distinctive from the inside — the autistic pull toward routine versus the ADHD drive toward novelty, autistic social confusion versus ADHD social impulsivity — aren't always neatly separable in a real person. And as covered above, 30–50% of autistic people also have ADHD. So the answer to "which one is it?" is often "both."

A few patterns that can help orient the question:

Leans more toward autism:

• Strong need for routine and predictability; changes feel genuinely threatening, not just inconvenient
• Social confusion — not knowing the implicit rules — rather than social impulsivity
• Deep, sustained, specific interests
• Sensory sensitivities that drive significant avoidance or seeking behaviour
• The persistent sense of having always been "different" in a way that's hard to articulate

Leans more toward ADHD:

• Difficulty across tasks in general, not primarily in social situations
• Novelty-seeking; boredom that's physically hard to tolerate
• Impulsivity — acting or speaking before thinking
• Attention that's hard to direct, rather than hard to shift away from a specific focus
• Executive function difficulties as the main presenting problem

Points toward both:

• All of the above, in tension with each other
• Needing routine and simultaneously craving novelty
• Emotional dysregulation that's more intense than either condition alone typically produces

The most useful takeaway: the question "which one?" can be less productive than pursuing proper assessment. A clinician assessing only for one condition may miss the other.

How to get assessed for both autism and ADHD

If your child has one diagnosis and you're seeing significant traits of the other, ask the question directly with your GP or paediatrician. You can request a referral for further assessment; having an existing neurodevelopmental diagnosis often makes this easier, not harder. For the ADHD assessment pathway, the ADHD hub covers this in detail.

For school support, both conditions need to be named in any EHCP or SEN support plan; support built around one and not the other will have gaps. The EHCP guide covers how to ensure both are reflected in provision.

---

This article is part of the Neuroequipped Autism guide. For ADHD specifically, see the ADHD hub. For autism assessment, see Autism assessment: NHS and private options. For autism in girls, see Autism in girls: why it looks different. For support levels and what "high-functioning" actually means, see What is high-functioning autism?.

Neuroequipped provides research-grounded information for parents and educators. It is not medical advice.