Can a child have both autism and ADHD?

Yes. A child can have both autism and ADHD; since 2013 UK clinicians can diagnose them together, and around half of autistic children also have ADHD. NICE says an ADHD diagnosis must not delay an autism referral. The two conditions sit alongside each other often enough that some people use the informal term "AuDHD" for the combination, though that is a shorthand rather than a separate clinical label.

Why so many people still say "only one"

The myth has a date on it. Until 2013, the main diagnostic manual used by clinicians (DSM-IV) actually forbade diagnosing autism and ADHD in the same person. That rule was dropped when DSM-5 became the first manual to allow a joint diagnosis. So when an older relative, or even an out-of-date web page or clinician, tells you a child can only have one, they are repeating a rule that has not applied for more than a decade. Today the NHS lists ADHD among the conditions that commonly co-occur with autism.

The NICE rule that protects the second referral

This is the part most parents are not told. Current UK guidance is clear that having one diagnosis must not be used to refuse or delay assessing for the other. NICE's autism guideline (CG128) tells clinicians not to exclude or delay a referral for possible autism because of an earlier ADHD diagnosis, and to check for co-existing conditions, including ADHD, as part of an autism assessment. So if you are told "they already have ADHD, so it is not autism", you can point to CG128 by name.

It matters in practice because the traits overlap and one can hide the other:

• a very active, impulsive child may be read as "just ADHD", and the autism missed;
• a quietly autistic child who masks at school may have ADHD attention difficulties put down to autism alone;
• where signs could be caused by either condition, both deserve looking at, not a single label that closes the door.

How the assessment route works

On the NHS, many areas now run a single neurodevelopmental pathway. NHS England's payment guidance expects services to assess children for autism, ADHD, or autism and ADHD combined, and for autism teams to have the expertise to look at conditions that commonly co-occur. Whether your area does one combined assessment or two separate referrals varies locally, which is covered in can my child be assessed for autism and ADHD at the same time? If you are weighing up which traits you are seeing, it can help to read what the difference between autism and ADHD is.

This page is general information, not clinical or legal advice.