ADHD, Autism, or Both? What the Overlap Actually Looks Like

By Dr Floriana Reinikis, Consultant Clinical Psychologist | Oasis Psychological Services | Ashford, Kent

The question I’m asked most often, in initial consultations, in messages from parents, in conversations with adults who’ve spent months researching before they’ve spoken to anyone clinical, is some version of this:

“I’ve been reading about ADHD and autism for weeks. Sometimes I think it’s one. Sometimes I think it’s the other. Sometimes I think it might be both. I honestly can’t tell.”

What I want to say to anyone in that position is this: the difficulty you’re having is not a sign that you’re confused or that you’re overthinking it. It’s a sign that these two conditions are genuinely harder to distinguish than most people expect, that they share more common ground than the internet tends to make clear, and that for a significant number of people, both are present at the same time. The uncertainty you’re sitting with is a reasonable response to real clinical complexity. Not a reflection of anything lacking in you.

Let me try to make it clearer.

They are different things. But the differences aren’t always where people expect them to be.

When people think about how ADHD and autism differ, they often think about attention and social skills. The picture they have in mind is something like: ADHD is the one where you can’t sit still and can’t concentrate, and autism is the one where you struggle socially. That picture isn’t wrong exactly, but it’s so simplified that it ends up being more misleading than helpful.

Here’s what I actually find more useful.

ADHD is primarily a condition of self-regulation. It affects how the brain manages attention, impulse control, emotions, and the executive functions that underpin everyday life: starting tasks, organising, planning, following through, and managing time. These are not simply skills that can be learned with more effort or willpower. They reflect genuine neurological differences in how the brain regulates itself.

One of the things that makes ADHD harder to recognise is how inconsistent it can look from the outside. The same person who cannot make themselves begin a piece of work, despite genuinely wanting to and understanding the consequences of not doing it, can spend hours completely absorbed in something they find fascinating. That inconsistency is not a character flaw or a motivation problem. It reflects the way executive functioning in ADHD is sensitive to interest, novelty, and emotional engagement in ways that standard demands and deadlines don’t always activate. Understanding that distinction changes how you make sense of the difficulties, and how you respond to them.

Autism is something broader and different in kind. It’s about how a person experiences and processes the social world, sensory input, communication, routines, and change. And here is where I think the most important clarification needs to happen, because the word “social” tends to conjure the wrong image.

When we talk about social differences in autism, we are not talking about someone who doesn’t want connection, or who doesn’t care about other people. Many autistic people want connection deeply. What’s different is the underlying architecture of how social information is processed, how unwritten rules are read, how sensory input from the social environment is experienced. Research has increasingly shown that autistic people often feel others’ emotions intensely, while finding the cognitive interpretation of social signals more effortful. The difficulties are not about caring. They’re about processing.

And sensory experience sits at the heart of the autistic experience in a way that it simply doesn’t in ADHD. Sounds, textures, light, the feeling of clothing, the unpredictability of other people’s behaviour, all of this can register at a level of intensity that non-autistic people don’t experience in the same way. This isn’t sensitivity in the everyday sense of the word. It’s a nervous system that processes sensory information differently, and that can reach a point of overload with real and significant consequences for daily life.

Now here’s where it gets complicated. And where I think the most important thing needs to be said.

These two conditions share enough territory that they can be genuinely difficult to tell apart, especially when you’re trying to understand someone from the outside, and especially when masking is involved.

Both can involve difficulty with emotional regulation. Both can involve difficulty in social situations. Both can involve intense focus on areas of interest. Both can involve anxiety. Both can involve a significant gap between how someone presents to the world and what it actually costs them to maintain that presentation.

And crucially: both can be present in the same person at the same time. Research confirms that ADHD and autism co-occur in a meaningful proportion of people. For a long time, clinical guidelines actually prevented both diagnoses from being given together, which meant that many people received one explanation when both were present. That has changed, and a thorough assessment now needs to hold both possibilities open rather than settling on an answer before the full picture has been gathered.

You may have come across the term AuDHD, particularly on social media and in online communities, used to describe the experience of living with both ADHD and autism. If you’ve searched for it, you’re not alone. It’s worth knowing, however, that AuDHD is not a clinical term. In clinical practice, the correct language is a co-occurring presentation of ADHD and autism, or a dual diagnosis of both. The community term exists because the experience of having both is genuinely its own kind of experience, not simply ADHD and autism added together, and that’s something a thorough assessment needs to take seriously.

What I want to do now is show you what that overlap actually looks like in real life, because I don’t think explaining it in the abstract is enough.

What it looks like when both are present

Think about a child who needs constant novelty to stay engaged. Who finds repetitive or predictable tasks almost impossible to sustain. Who moves from one thing to the next, whose energy visibly spikes when something new and interesting arrives. That’s a recognisable ADHD picture.

Now imagine that same child falls completely apart when you suggest changing the plan you agreed that morning. When the usual route to school is closed and you have to take a different road. When a visitor is coming for dinner and the routine of the evening will be different. The resistance isn’t a tantrum. It’s genuine distress. The world has become unpredictable in a way the nervous system cannot absorb.

This is one of the tensions I see most often in the young people and adults I assess, and it’s one of the clearest signs that both profiles may be worth exploring carefully. The ADHD part of the picture pulls towards stimulation and change. The autistic part relies on predictability and sameness for genuine safety and regulation. From the outside, this looks contradictory. From the inside, it is exhausting. And the person often cannot explain it, because neither pull is a choice.

Or think about an adult who interrupts in conversations, who talks over people, who shares things impulsively before they’ve considered whether this is the right moment. That reflects the impulsivity and difficulty with self-regulation that ADHD brings to social situations. But the same person may also find it harder at times to read what a colleague meant by a certain comment, or may not always pick up on the shift in someone’s tone that signals irritation, and finds group social situations not just tiring but genuinely confusing in a way that doesn’t feel like distraction. That’s something different. When both are present together, the picture becomes more complex than either alone, and understanding what is driving what matters enormously for the kind of support that will actually help.

And then there is the emotional picture, which is where things can feel most bewildering for the people I work with.

ADHD emotional responses tend to be rapid and intense: easily triggered, difficult to modulate in the moment, and often relatively quick to resolve once the moment has passed. Some people with ADHD also describe a heightened sensitivity to perceived criticism, rejection, or failure, an emotional response that can feel disproportionate from the outside but is experienced as overwhelming from the inside. You may have seen this referred to online as Rejection Sensitive Dysphoria, or RSD, a term that was popularised following an article by William Dodson in 2015. It is worth understanding that term in its proper context. Rejection sensitivity as a concept has a much longer history in psychology, and it is not specific to ADHD. It appears across many different conditions and life experiences, including autism, anxiety, trauma, and depression. It is not a diagnostic criterion for ADHD, and not everyone with ADHD experiences it. But for those who do, it can be a significant part of their picture, and at Oasis Psychological Services we always try to explore what lies beyond the diagnostic criteria, because understanding the whole person, their experiences, their strengths, and their difficulties, gives us a far more complete and useful picture than the criteria alone.

Autism brings something different to the emotional picture. Emotional responses are often more closely connected to sensory experience. When the environment has become too much, when there has been too much noise, too much social demand, too many unexpected changes across the course of a day, what follows can look like a sudden and apparently disproportionate emotional response. But from the inside, it isn’t sudden at all. It’s the result of accumulated overload finally exceeding what the system can hold.

Many autistic people also experience a difficulty identifying and naming what they’re feeling. Not the absence of emotion, but a kind of internal blurriness where something is clearly wrong and clearly intense, and yet the emotional experience isn’t easily accessible in a way that allows it to be named, explained, or communicated. When this sits alongside ADHD’s fast emotional escalation, you get someone who erupts intensely and cannot tell you why, and possibly cannot tell themselves. That combination deserves careful clinical attention, not a simplified explanation.

Why this matters so much

The reason I think it’s worth being this specific about the overlap is not just clinical accuracy. It’s because misidentification has real consequences.

The child who is assessed for ADHD and given strategies for attention and impulsivity, when what is also driving their experience is a sensory world that is genuinely overwhelming and a social environment that is genuinely confusing, will not be fully served by those strategies. The adult who is told their difficulties are primarily autistic, when there is also an ADHD executive functioning picture that is making initiation, organisation, and emotional regulation significantly harder, is working with an incomplete map of themselves.

And the people most likely to have both missed are often those who are intellectually able, who have worked very hard to manage, who appear to be coping from the outside while carrying a great deal on the inside. The strategies work, until they don’t. The point at which they stop working, burnout, anxiety, a period of significant difficulty, is often what finally brings someone to us.

What a thorough assessment does with all of this

At Oasis Psychological Services, we don’t begin an assessment with a conclusion and work backwards towards it. We begin with the person. Every assessment pathway starts with an initial consultation, where we screen for ADHD, autism, and anxiety, because we want to understand what is present, and how these may be interacting, before deciding on the right pathway forward. That conversation shapes everything that follows.

For adults seeking a private ADHD assessment in Kent or an adult autism assessment, that means taking time to understand not just where the difficulties are, but how you’ve adapted, compensated, and managed across your life. Masking can make both profiles much harder to see, and a thorough assessment needs to look underneath the surface presentation rather than taking it at face value.

For families seeking a child autism assessment or a child ADHD assessment in Kent, we draw on information from parents, school, and the young person themselves, because the gaps between how a child presents in different environments are often as informative as the picture in any single one.

If you’ve found yourself reading this and recognising something, in yourself or in your child, we’d be glad to start a conversation. That’s all it needs to be at first. You can reach our team at info@oasispsychologicalservices.co.uk or call us on 07307 385472.

A diagnosis is a beginning, not an end.

Dr Floriana Reinikis is a Consultant Clinical Psychologist, Accredited CBT Psychotherapist, and ADDCA-accredited ADHD Coach. She is the founder of Oasis Psychological Services and a training provider for ADHD assessment to NHS trusts across the UK.