My child has autism and ADHD: is that genetic?

Parents often ask me this in clinic. Their child has autism and attention deficit hyperactivity disorder (ADHD). They want to know if it is genetic, and whether a test could tell them more. This note gives a short answer. It then explains what the answer does and does not mean for one family.

The short answer

Yes, genes play a part. Genes contribute to autism. They also contribute to ADHD. Neither condition is caused by one gene. Parenting does not cause either.

A large study published in September 2026 looked at autistic people who also had ADHD, anxiety or depression (1). It suggests that ADHD in autistic people goes with its own genetic influences. These are the same kind of influences that are linked to ADHD in people who are not autistic. They do not seem to be the same influences that are linked to autism itself.

These findings describe large groups of people. They do not tell you why your child has ADHD.

What the study found

Adeniran Okewole and colleagues, led from the Autism Research Centre in Cambridge, used data from a large US research cohort of autistic people and their families. They studied 74,204 autistic people of European ancestry. Parents, or the autistic person, reported that 37% had ADHD. Genetic data were available for 17,582 people.

The researchers used polygenic scores. A polygenic score is one number that adds up many small, common genetic differences. Each difference has a tiny effect on its own. Higher polygenic scores for ADHD, and for depression, were linked with higher scores in all three groups of co-occurring conditions that the researchers defined. The polygenic score for autism was not linked with any of them. The study put ADHD in one group with disruptive behaviour disorders, so it did not look at ADHD on its own.

In the families where the child and both parents had genetic data, the parents’ scores were not linked with the child’s scores.

The full findings are in my post Autism with ADHD, anxiety or depression: what the genes show.

What “genetic” means here

When researchers say ADHD is genetic, they mean this. Across large groups of people, genetic differences explain part of why some people have ADHD and others do not. This is a statement about populations.

It does not mean that one gene causes ADHD in your child. It does not mean that anyone is to blame. Environment also matters. If a parent or sibling also has ADHD, that fits with a shared genetic background. It does not prove one, because families also share their home and their daily routines.

So the honest answer to “Is it genetic?” is “Partly, in the way that applies to many people, and we cannot say how much for your child.”

Will a genetic test tell us more?

Polygenic scores are research tools. They are not used in National Health Service (NHS) clinical care for autism or ADHD. They cannot diagnose ADHD, predict it, or rule it out for one child. This includes scores in commercial genetic reports that some families bring to clinic.
NHS genetic testing is different. It looks for rare genetic changes. It is offered when there are particular features, for example a learning disability, global developmental delay, unusual physical features, epilepsy or a relevant family history. Autism and ADHD together are not, on their own, a usual reason for NHS genetic testing.
A test result will not change this answer. A normal result does not mean genes are not involved. A test cannot say which of your child’s conditions are genetic and which are not.
Support does not depend on a test. ADHD is assessed from your child’s history, from observation, and from information from home and school. Support is based on what your child needs.

My guide Genetic testing in autism: what UK results can and cannot tell you explains who is offered NHS testing, and what results can and cannot tell you.

Limits of the evidence

The genetic analyses included only people of European ancestry. Many UK families have South Asian, African, Caribbean, mixed or other ancestry, so the findings may not apply to them.
All the data came from one US research cohort.
Diagnoses were reported by parents or by the autistic person. They were not checked against medical records.
The study shows links across thousands of people. It does not show that any one genetic difference causes ADHD.
This is one study. Other studies need to confirm it.

What this means in clinic

Assess ADHD on clinical grounds, alongside the autism assessment. National Institute for Health and Care Excellence (NICE) guidance on autism in children and young people already asks clinicians to look for coexisting conditions.
Do not assume that attention difficulties are simply part of the autism.
Do not use polygenic scores to diagnose, predict or rule out ADHD.
Refer for genetic testing when the child meets NHS criteria, not because of ADHD alone.
Avoid telling a family that their child has “the ADHD gene” or “the autism gene”. No single gene explains either condition in most children.

What this means for families

Autism and ADHD often occur together. This is common and is not a sign that something was missed or that anyone is to blame.
Genes are part of the explanation, in a way that applies to groups of people. They do not give a forecast for your child.
You do not need a polygenic score or a commercial genetic report for your child.
If you are worried about your child’s attention, activity level, mood or behaviour, tell your general practitioner (GP), your paediatrician or your child’s school.

Reference

Okewole A, Bourque VR, Koko M, et al. Common genetic variants are associated with increased likelihood of latent co-occurring neurodevelopmental and mental health factors among autistic individuals. Molecular Psychiatry. Published online 12 September 2026. doi:10.1038/s41380-026-03880-1

Dr Odet Aszkenasy is a Neurodevelopmental Paediatrician and wrote this note.