ADHD vs Autism: How to Tell the Difference (and Why So Many People Get Misdiagnosed)

"Is It ADHD, Autism, or Both?"

I hear this question constantly. In mentoring sessions, in DMs, in those 2am Google spirals that somehow end with you filling out three different online quizzes and feeling more confused than when you started.

And honestly? The confusion is completely understandable. ADHD and autism share a surprising number of traits. They are both neurodevelopmental conditions. They both affect executive function, social interaction, and sensory processing. And they co-occur so frequently that research suggests 50-70% of autistic people also meet the criteria for ADHD (Leitner, 2014, Frontiers in Psychiatry). So when someone says "I cannot tell if this is ADHD or autism," they are not being silly. The overlap is genuinely massive.

But here is the thing: they are still different conditions. They have different underlying mechanisms, they present differently in key areas, and getting the wrong diagnosis (or only half the picture) can mean you end up with support strategies that do not quite fit. Which is incredibly frustrating when you are already struggling.

So let us break it down. What is actually different, what overlaps, and what to do if you think you might have been misdiagnosed.

The Core Difference (in Simple Terms)

I think the most helpful way I have ever heard it explained is this:

ADHD is primarily a difficulty with regulating attention, impulses, and activity levels. Autism is primarily a difference in how you process social information, sensory input, and patterns.

Dr Russell Barkley describes ADHD as fundamentally a disorder of self-regulation and executive function. Your brain struggles to manage attention, filter impulses, and organise behaviour over time. It is not that you cannot pay attention. It is that your brain struggles to direct attention where it needs to go, when it needs to go there.

Autism, on the other hand, is characterised by differences in social communication and interaction, alongside restricted and repetitive patterns of behaviour and interests (as defined in the DSM-5 and ICD-11). It is a difference in how the brain processes the social world and makes sense of patterns, routines, and sensory experiences.

Now, do those things overlap in real life? Absolutely. Which is exactly why it gets so confusing.

Where ADHD and Autism Look Similar

This is the bit that catches people out. Because on the surface, quite a few traits look almost identical:

• Difficulty with social situations. ADHD can make you interrupt, zone out mid-conversation, or miss social cues because you were not paying attention. Autism can mean you genuinely struggle to read those social cues in the first place. The outcome looks the same. The reason behind it is different.
• Sensory sensitivities. Both ADHD and autism can involve heightened sensitivity to noise, light, textures, or smells. If you want to dig deeper into this, I have written about ADHD and sensory processing specifically.
• Executive dysfunction. Planning, organising, starting tasks, finishing tasks. Both conditions can make all of these feel like climbing a mountain in flip-flops.
• Emotional intensity. Big feelings, quick reactions, difficulty calming down. Both ADHD and autism involve emotional regulation challenges, though they show up in slightly different ways.
• Hyperfocus and special interests. ADHD hyperfocus tends to be more short-lived and driven by novelty. Autistic special interests tend to be deeper and more enduring. But from the outside, someone deeply absorbed in something looks the same regardless.
• Masking and camouflaging. Both ADHD and autistic people learn to mask their differences to fit in socially, which is exhausting and often contributes to burnout, anxiety, and depression. This is especially true for women with ADHD, who are frequently underdiagnosed for both conditions.

ADHD vs Autism: The Key Differences

Right, here is where it gets useful. Because despite all the overlap, there are some genuinely meaningful differences.

Obviously, not everyone fits neatly into these boxes. Humans are messy and complicated, which is sort of the point. But these patterns can be helpful starting points for understanding where your experiences might fit.

Why Misdiagnosis Happens So Often

Here is something that genuinely frustrates me as someone who works in this space: misdiagnosis between ADHD and autism is incredibly common, and it causes real harm.

A study published in the Journal of Attention Disorders (Kentrou et al., 2019) found that a significant number of autistic adults had previously received ADHD diagnoses without their autism being recognised. And it works the other way too. People with ADHD get misdiagnosed with anxiety, depression, or personality disorders because their ADHD traits get interpreted through the wrong lens.

There are a few reasons this keeps happening:

1. Outdated Stereotypes

The old image of ADHD as a hyperactive boy who cannot sit still, and autism as a non-speaking child who avoids all social contact, means that anyone who does not fit those stereotypes slips through the cracks. Women and girls are particularly affected. The NICE guidelines (NG87) now acknowledge gender differences in presentation, but in practice, many assessors still rely on outdated frameworks.

2. Masking Hides the Real Picture

If you have spent years learning to camouflage your traits, you might present as "fine" in an assessment. I have worked with clients who masked so effectively during their ADHD assessment that the clinician did not pick up on autistic traits sitting right underneath. And vice versa.

3. Assessments Are Often Siloed

In the UK, ADHD assessments and autism assessments are typically done separately, often by different teams, in different services, with different waiting lists. So even if a clinician spots traits of the other condition, they might not be qualified or funded to assess for it. This means people can fall into a gap where only half the picture gets identified.

4. Symptom Overlap Creates Confusion

As we have already covered, so many traits look the same on the surface. Without a really detailed developmental history and careful questioning, it is easy for even experienced clinicians to attribute everything to one condition and miss the other.

If you are currently navigating the ADHD diagnosis process in the UK, I would strongly recommend mentioning any autism-related concerns to your assessor, even if you are not sure. It is always better to raise it and have it explored than to leave it unspoken.

Could It Be Both? Understanding AuDHD

Yes. Full stop. You absolutely can have both ADHD and autism, and actually, it is far more common than most people realise.

The term AuDHD (autism plus ADHD) has become widely used in the neurodivergent community to describe this dual experience. I have written a whole article about what AuDHD is and what it feels like, so I will not repeat everything here. But the short version is: having both conditions creates a unique internal experience where your ADHD brain and your autistic brain are often pulling in completely opposite directions. Your ADHD craves novelty while your autism craves routine. Your ADHD wants spontaneity while your autism needs predictability.

It is exhausting. But it is also really helpful to understand, because once you know what is happening, you can start building strategies that work with both parts of your brain rather than against them.

If this resonates, you might also find our guide on AuDHD mentoring support helpful. It covers what tailored support looks like when you are navigating both conditions at once.

Getting the Right Assessment in the UK

So what should you actually do if you think you might have been misdiagnosed, or if you suspect you have both conditions?

Ask Your GP for a Referral (or Use Right to Choose)

You can ask your GP to refer you for an autism assessment through the NHS. The waiting lists are long (often 1-3 years depending on your area), but you can also use Right to Choose to access an assessment through a private provider funded by the NHS. We have a detailed guide on how ADHD diagnosis works in the UK that covers this process.

Prepare for Your Assessment Properly

Write down your experiences in detail before your assessment. Think about childhood traits, sensory experiences, social difficulties, routines, and how you cope with change. Bring examples. If you can, ask a parent or someone who knew you as a child to provide information too. The more detail the assessor has, the more accurate the outcome.

Be Honest About Masking

This is a big one. If you mask, say so. Tell the assessor that your day-to-day presentation might not reflect your internal experience. Explain the strategies you use to appear "normal" and the cost those strategies have on your energy and mental health. A good assessor will take this into account.

Seek a Clinician Who Understands the Overlap

Not all assessors are equally experienced with the ADHD-autism overlap. If you can, look for clinicians who specialise in neurodevelopmental conditions broadly, rather than only ADHD or only autism. This gives you the best chance of getting the full picture.

What Getting the Right Diagnosis Actually Changes

I have seen this so many times in my work: someone gets the right diagnosis (or discovers they have both ADHD and autism) and suddenly, years of confusing, frustrating experiences click into place.

They understand why certain strategies never worked for them. Why CBT felt pointless. Why they could not just "try harder" at things other people found easy. Why they felt exhausted after social events even though they genuinely enjoyed being there.

Getting the right diagnosis is not about putting yourself in a box. It is about finally having a map that makes sense of the terrain you have been walking through your whole life.

You Deserve Support That Actually Fits

If you have read this far and you are thinking, "this is me," or "I think I might have been misdiagnosed," or even just "I need help figuring this out," please know that you do not have to do this alone.

Whether you are exploring whether it is ADHD, autism, or both, I can help you make sense of your experience and build practical strategies that work with your brain. Mentoring is not about diagnosis. It is about understanding yourself better and getting the support you actually need.

Book a free discovery call and let us figure this out together. No pressure, no judgement, just a conversation about where you are and how I can help.