ADHD vs. autism in adults: differences, overlap and how to tell them apart

If you have ever read a list of ADHD traits and thought "that's me," then read a list of autism traits and thought the same thing, you're not imagining the overlap. The two share a lot of surface behavior and often turn up in the same person.

Here's how to tell them apart, and what to do if you think you might have one or both.

What is the difference between ADHD and autism?

ADHD (attention-deficit/hyperactivity disorder) is a neurodevelopmental condition defined by inattention, hyperactivity and impulsivity ^[1]. In practice that means trouble staying on task or organized, restlessness or excessive talking, and acting before thinking: interrupting, intruding, finding it hard to wait your turn. Symptoms begin in childhood and usually continue into adulthood ^[1].

Autism is also a neurodevelopmental condition, but its core is different. Under the DSM-5 criteria, an autism diagnosis needs persistent differences in social communication (back-and-forth interaction, nonverbal communication, and building and keeping relationships) plus at least two kinds of restricted or repetitive patterns ^[2]. Those patterns include repetitive movements or speech, insistence on sameness, intense focused interests, and over- or under-reaction to sensory input like sound, texture, light or pain ^[2].

Put simply, ADHD is about regulating attention and impulses. Autism is about how you take in the social and sensory world, and how much you need it to be predictable.

Can you have ADHD and autism at the same time?

Yes. For years you officially couldn't. The DSM-IV, the diagnostic manual used from 1994, had a rule that stopped clinicians from diagnosing ADHD in someone who was autistic, so they had to pick one ^[3]. The DSM-5, published in 2013, removed that rule, and the two can now be diagnosed together ^[3].

People sometimes call the combination "AuDHD." It's an informal term, not a separate diagnosis. A clinician would record two diagnoses: autism and ADHD.

How common is it to have both?

Quite common, though the exact figure depends on how a study was done.

• A 2021 meta-analysis of 63 studies found current ADHD in 38.5% of autistic people and lifetime ADHD in 40.2% ^[4]. The rate shifted with age, intellectual disability, where people were recruited and which diagnostic criteria were used.
• Going the other way, a 2020 review of 22 studies with nearly 62,000 participants found that 21% of children and teenagers with ADHD met the threshold for autism ^[6]. The figure was 19% in community samples and 24% in clinical ones.
• In a Swedish register study of about 1.9 million people, autistic people had roughly 22 times the odds of also having ADHD ^[7].

The overlap also shows up as traits, not only diagnoses. In the same 2020 review, children with ADHD scored far higher on autism trait rating scales than children without ADHD ^[6]. So if you have ADHD and some autism traits sound familiar, that fits the research, whether or not you're also autistic.

Why so much overlap? Genes are part of it. In that same Swedish study, the full siblings of autistic people had about 4.6 times the odds of ADHD, and the odds rose with how closely related people were ^[7]. The authors concluded that genetic factors play a role in the two showing up together, while noting that shared family environment may also contribute.

Where do ADHD and autism look alike?

Both begin early and both can strain work and relationships. From the outside, a lot of behavior can look identical. The diagram below sorts some common traits by where they usually belong.

Same behavior, different reasons

This is where the two really come apart. A good assessment asks about the reasons behind a behavior, not only the behavior itself. Here are a few everyday examples of one behavior with two possible explanations.

Say you skip a work party. With ADHD, you might have forgotten it was tonight. With autism, you might have known all week and dreaded the noise and small talk. Same outcome, different engine underneath. And the support that helps is different too.

Questions that can help you tell them apart

You can't diagnose yourself, but you can notice which pattern fits better. These questions follow the official descriptions of each condition. Try answering them with real examples from your week.

• When you lose focus, is it mostly on tasks that bore you, with your attention pulled toward whatever else is going on? That leans toward ADHD ^[1]. Or do you lock onto a few interests so deeply that other things fall away? That is closer to autism ^[2].
• When conversations go wrong, is it because you drifted off or jumped in too early ^[1]? Or because it's hard to read what people mean from their tone and faces ^[2]?
• Do sounds, lights, smells or textures feel physically uncomfortable, not just distracting? Sensory over- or under-reaction is part of the autism criteria and not part of the ADHD criteria ^[2].
• Does an unexpected change of plan upset you because it breaks a routine you rely on? Insistence on sameness is an autism trait ^[2].
• Can you remember these traits from childhood? Both conditions start early ^[1][2], so a clinician will ask. If the traits only began recently, something else may be going on.

If you answer "yes" on both sides, that's not unusual. It's one of the reasons so many people end up assessed for both.

What does it look like to have both?

When both are present, the traits can pull in different directions. Autism can bring a strong need for sameness ^[2], while ADHD can make it hard to stay organized and on task ^[1]. So, for example, you might rely on a routine to feel steady and still struggle to keep that routine going.

Picture a workday. You plan it carefully because surprises throw you, then lose the plan under a pile of half-started tasks. A colleague changes the meeting time, and you're rattled for an hour. Neither condition alone fully explains a day like that, and it's exactly the kind of pattern worth describing to an assessor.

Having both can also make each one harder to recognize. The authors of the 2021 meta-analysis urged clinicians to look closely for ADHD in autistic people, especially children and teenagers ^[4]. If you already have one diagnosis and some of your experiences still don't fit it, that's a reasonable thing to bring up.

Is support different for ADHD and autism?

Yes, and that's the practical reason the distinction matters. Standard treatment for ADHD includes medication and talking or behavioral approaches such as cognitive behavioral therapy, with school support for children ^[1]. Researchers are also studying newer options like mindfulness and neurofeedback ^[1].

Autism works differently. The NHS describes autism as something you're born with, not an illness, with no treatment or cure for autism itself ^[15]. Support is about understanding how you work and changing things around you, for example a quieter desk or written instructions instead of verbal ones.

Both often come with company. Anxiety and depression are common alongside ADHD ^[1], and the NHS lists both as more likely in autistic people ^[15]. Mention them to a clinician too. Co-occurring conditions can make ADHD harder to recognize and treat ^[1], so the full picture helps.

Why are so many adults, especially women, diagnosed late?

Both conditions start in childhood, but many people get no diagnosis until adulthood, or never. Worldwide, an estimated 2.58% of adults have ADHD that began in childhood, and 6.76% have ADHD symptoms above the diagnostic threshold ^[8]. In the United States, the CDC estimated that 2.21% of adults are autistic, about 5.4 million people (a modeled estimate from 2017 data) ^[9].

Sex differences are a big part of the late-diagnosis story. For autism, a meta-analysis of 54 studies found the true ratio of boys to girls is closer to 3 to 1 than the often-quoted 4 to 1, and concluded that girls who meet the criteria are at greater risk of not being diagnosed ^[10]. For ADHD, a 2020 expert consensus statement found that girls and women are under-recognized, often show a quieter, more inward presentation, and may use coping strategies that hide their symptoms ^[11].

Hiding traits has a name in autism research: camouflaging. In a study of 92 autistic adults, people described masking and compensating to fit in, and reported exhaustion as one of the costs ^[12]. The DSM-5 itself notes that autistic traits may be masked by learned strategies later in life ^[2].

How do ADHD and autism screeners differ?

Screening questionnaires are built around each condition's core traits, so they ask quite different questions.

The best-known adult ADHD screener is the World Health Organization's Adult ADHD Self-Report Scale (ASRS). It has an 18-question symptom checklist and a six-question screener drawn from it. In the original validation study with 154 adults, the six-question version correctly identified 68.7% of people with ADHD and correctly cleared 99.5% of people without it ^[13].

For autism traits in adults, a widely used questionnaire is the 50-question Autism-Spectrum Quotient (AQ). In the study that introduced it, 80% of autistic adults scored 32 or more, compared with 2% of the comparison group ^[14].

Our ADHD test asks how often you've experienced 18 common patterns over the past six months, in the style of the ASRS. Our autism test asks 20 questions about social life, communication, focus, routine and the senses, following the style of established adult screeners such as the AQ. Taking both can show you which pattern fits you better, or whether both seem to.

A high score on either one is a reason to talk to a professional, not a diagnosis. Questionnaires can't see your childhood, your context or the reasons behind your answers.

How do I get assessed for ADHD, autism or both?

There is no single test for ADHD ^[5], and autism is diagnosed against the DSM-5 criteria by a trained clinician ^[2]. Services vary a lot by country, but the path usually looks something like this.

It helps to arrive prepared. Things worth bringing:

• Specific examples from work, home and relationships, ideally written down as they happen over a few weeks.
• School reports, old diaries or anything else that shows what you were like as a child.
• Someone who knew you growing up, if they're willing to talk to the assessor or fill in a form.
• Your screener results, with a note that they are a starting point and not a diagnosis.
• What you've already tried, such as apps, routines or workplace changes, and how well each one worked.

If you've already been diagnosed with one condition, it's worth asking whether the other was considered. Since 2013 there has been no rule against having both ^[3].

If you're mainly wondering about ADHD, our guide to signs of ADHD in adults goes deeper into how it shows up at work, at home and in relationships.

Or go straight to the autism traits test.