A lot of people arrive certain they have one of these and unsure about the other. Often they are right about both.
This page covers when a combined assessment is worth considering, how it works in practice, and what it costs compared with being assessed twice.
How Often Do ADHD and Autism Occur Together?
Frequently. Research puts ADHD in roughly 28 to 37 per cent of autistic people when you pool studies together, and the figure rises substantially - some studies report up to 85 per cent - in clinical groups like the people who actually come for assessment.
Whichever end of that range applies, the practical point is the same: if you are being assessed for one, the other is worth having in scope.
Why Assessing One Alone Can Miss the Other
The two conditions share surface features and have different underlying causes. Difficulty following a conversation can be inattention or it can be social communication difference. Needing routine can be autistic preference or it can be a strategy built to manage ADHD.
A clinician looking only for one will tend to find it, and will reasonably attribute everything they see to it. That is how people end up diagnosed with one condition, treated for it, and still struggling with the part nobody looked at.
Signs Both Might Be Relevant
- You were assessed for one condition and the result explained some of it but not all
- Treatment for ADHD helped your focus but not your social exhaustion
- You recognise yourself in descriptions of both, and have assumed you must pick one
- A family member has one diagnosis and you see both patterns in yourself
- You mask heavily in social settings and are depleted afterwards
How a Combined Assessment Works
It is not two separate appointments stapled together. The clinician gathers one developmental history and one picture of current functioning, then tests it against both sets of criteria rather than one.
In practice that means a longer assessment and often more than one clinician, because autism diagnosis is normally multidisciplinary. What it avoids is paying twice for overlapping work and telling your story from scratch a second time.
What It Costs
An autism assessment with us is £1,900. Where both conditions are in scope the assessment is longer, so the fee differs from a single-condition assessment, we will quote you before you book rather than after.
Compare that with the alternative of two separate private assessments at two clinics, which usually costs more in total and always costs more in time.
Can You Start With One and Add the Other?
Yes, and plenty of people do. If ADHD is clearly the more pressing issue, being assessed for that first is perfectly reasonable, particularly if medication is what you are seeking.
Tell the clinician that autism is also a question, though. It changes what they ask and what they record, and it makes a later autism assessment much easier if the groundwork is already there.
What Happens If Only One Is Diagnosed?
That is a common and useful outcome. The report will set out what was found, what was considered and ruled out, and why, which is precisely what makes a report worth having.
Being told clearly that you do not meet the criteria for one condition is not a wasted assessment. It narrows the question, and it stops you spending another two years wondering.
Does a Combined Diagnosis Change Treatment?
It can change it considerably. ADHD medication may still be appropriate, but the support that helps with autistic burnout or sensory load is different, and adjustments at work or university are framed differently too.
Getting the full picture matters more than getting a label, which is the honest argument for assessing both together where both are genuinely in question.
Thinking about booking? Our private autism assessment is £1,900 and includes the full assessment, the written diagnostic report and a letter to your GP.
You can see what is included and book on our autism assessment page, or call and ask us anything first, including whether an assessment is the right step for you at all.
Conclusion
ADHD and autism overlap often enough that assessing one without considering the other risks a partial answer. If both feel relevant to you, say so at the point of enquiry and have the assessment scoped properly from the start.
If you are not sure whether both apply, that is a reasonable thing to ask us about before booking anything. We would rather have that conversation first than assess for the wrong thing.
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