ADHD and autism, and the overlap that delays diagnosis

If you have ever been assessed for ADHD and come away feeling that the answer explained a lot but not everything, there is a reasonable chance that autism is part of what was missed. The reverse is also true. Adults who receive an autism diagnosis in their thirties often go on to recognise an ADHD pattern that sits alongside it.

The two conditions are neurologically distinct but they co-occur far more often than chance would predict. UK clinical samples typically find between twenty and fifty percent of adults with ADHD also meet criteria for autism. The overlap is not a curiosity. It materially changes what helps, what does not, and what the treatment plan should look like.

Why they are so often confused

ADHD and autism can produce some surface-level similarities. Both can make social conversation effortful. Both can make transitions between tasks hard. Both can look like burnout at the end of the day. Both frequently involve sensory sensitivities, sleep difficulties, and high levels of background anxiety.

The underlying mechanisms are different, though. ADHD is fundamentally about attention regulation and impulse control. Autism is fundamentally about social communication differences and a preference for predictability and clear rules. Someone with ADHD can find small talk exhausting because their attention keeps sliding away. Someone with autism can find it exhausting because the unwritten rules of who speaks when and how much self-disclosure is appropriate are genuinely opaque. Someone with both often experiences both problems simultaneously, which is why they can feel worse than either one alone.

Why it matters for treatment

Stimulant medication is often transformative for ADHD symptoms. It can also unmask autistic features that were being covered by ADHD-related distraction. When the attention system calms down and the person can actually think in a straight line, sensory sensitivities, social fatigue, and a need for routine can become more prominent. That is not medication making things worse. It is medication making the underlying picture clearer.

This matters because if we only treat the ADHD and ignore an underlying autism profile, the person can be left feeling that their medication is working on paper but they are still exhausted at the end of every day. The answer is usually not more medication. It is working out that the remaining exhaustion is doing the job of a differently-wired nervous system in a world not built for it, and finding environmental and interpersonal strategies to manage it.

Masking and the late-diagnosed adult

A large proportion of adults with autism, particularly women and people assigned female at birth, have developed sophisticated social masking strategies. They watch how other people behave, build a mental script, and perform a version of socially acceptable behaviour that looks fluent from the outside but costs them enormously to maintain. Masking can be so effective that it completely hides autistic traits from observers and often from the person themselves.

ADHD in the same person often sits alongside masking as a second layer. The person has spent childhood and adolescence managing two neurodevelopmental differences at once, usually without naming either of them. When they are finally assessed, the ADHD often gets identified first, because its symptoms are more disruptive to day-to-day task completion. The autism sits one layer deeper.

What assessment should look like

A proper assessment in someone who has features of both should screen broadly. At LoveMyLife we use the RAADS-14 as a screener for autistic features alongside the ASRS-5 for ADHD. If the RAADS-14 score is elevated, we talk through it openly during the assessment. If a full autism diagnostic assessment is warranted, we explain the steps and costs honestly. We can do an ADHD diagnosis and treat it without insisting on a full autism assessment, but we flag the overlap so that you know what you are working with.

What to do if this is landing

You do not have to sort this out before you book. An ADHD assessment does not close down the autism conversation. It can be the beginning of it. If both conditions are relevant, we will see that together and plan accordingly. If the picture is purely ADHD, we will tell you that too.

Ready to start?

If this article has made you think it is time to find out, the next step is a short consultation with one of our ADHD-trained GPs.

Begin your consultation at this link. Online in 30 minutes, or in person at Westfield London.