Autism Is Genetic. That Doesn’t Mean There Is an “Autism Gene”.
One of the arguments I hear whenever I talk about the genetics of autism is this:
“But there’s no genetic test for autism.”
That’s true.
It also doesn’t contradict decades of research showing that autism has a strong genetic basis.
And if you’re autistic, have an autistic child, or are simply trying to sort through the enormous amount of autism information online, understanding this distinction matters. It can help you recognize when someone is explaining the science and when someone is using the complexity of the science to make a claim it doesn’t actually support.
Genetic Doesn’t Mean “One Gene”
I think part of the confusion comes from the word genetic itself.
People hear it and imagine a fairly simple process: scientists find a gene, test your DNA for it, and tell you whether you have a condition.
Autism doesn’t work that way.
Think about height. Height is strongly influenced by genetics, yet there isn’t one “tall gene” determining whether someone will be 5'2" or 6'2". Many genetic variants contribute.
Autism is considerably more complex, but the basic idea is useful.
Researchers describe autism as having a complex genetic architecture. That includes common genetic variants, rarer variants that can have larger effects, inherited variants, and de novo variants.
De novo simply means “new.” These are genetic changes that arise in an egg or sperm cell or very early in development rather than being inherited from a parent.
So something can be genetic without being inherited.
And something can have a strong genetic basis without there being one gene responsible for it.
Why This Matters When You’re Reading About Autism
This is where I think understanding the language becomes especially useful.
If someone tells you, “Scientists haven't found the autism gene, therefore autism isn't genetic,” you can immediately see the problem.
Modern autism research isn't looking for one universal autism gene.
Researchers are studying combinations of genetic variants, biological pathways, inherited variation, de novo variation and how all of these contribute to neurodevelopment.
Fun fact, they already know of over 128 traits that are foundational to autism. That doesn’t mean you have all of them.
The science has moved far beyond the simple question of “Is there a gene for this?”
In fact, modern genetics can ask much more interesting questions: Which variants are involved? How much does each contribute? Are they inherited? Did they arise de novo? What happens when many small genetic effects occur together? Do particular genetic pathways influence brain development?
Complexity isn't evidence that genetics doesn't matter.
The complexity is part of the genetics.
Genetics Is More Complicated Than We Were Taught
A 2026 study on PTSD offers an interesting example of just how sophisticated genetic research has become.
This was a PTSD study, not an autism study, so its findings should not be applied directly to autism. But researchers examining more than 144,000 people found that genetic liability could interact differently with different types of traumatic experiences.
That matters here for one reason: genetics is rarely as simple as “one gene causes one outcome.”
This is also important when autism and trauma get mixed together online.
Autistic people can absolutely experience trauma and develop PTSD. Trauma can affect behavior, mental health, masking, sensory regulation and quality of life.
But trauma affecting an autistic person is different from evidence that trauma created their autism.
Autism is a neurodevelopmental condition. PTSD requires exposure to trauma.
Those are different questions.
So Why Can’t We Test for Autism With DNA?
Because knowing that genetics contributes substantially to something is different from having a genetic test that can diagnose it in every person.
For some autistic people, genetic testing identifies a particular genetic condition or clinically significant variant associated with their neurodevelopment.
For many, it doesn’t.
Autism is currently diagnosed through developmental and behavioral assessment, not through one blood test or DNA test.
So these statements can both be true:
Autism has a strong genetic basis.
There is no single genetic test that diagnoses autism.
If you remember nothing else from this article, remember that.
The next time you hear “But they haven't found the autism gene,” you don't have to wonder whether that means the genetic research has somehow fallen apart.
There isn't supposed to be one autism gene.
What researchers are uncovering is much more complicated than that, and considerably more interesting.
Anyway, if you’d like to read more, here’s my rabbit hole…
Sources & Further Reading
News-Medical. Genetic risk for PTSD varies across different types of trauma. September 17, 2026.
European Journal of Psychotraumatology. Research examining gene-trauma interactions and PTSD across different categories of traumatic exposure, 2026.
Nature Medicine. Large-scale autism genetics research examining common and rare genetic variation across diverse ancestry populations, 2026.
Nature Genetics. Large-scale research identifying autism-associated genes through inherited and de novo genetic variation.
National Institute of Child Health and Human Development (NICHD). What causes autism spectrum disorder?
Centers for Disease Control and Prevention. Clinical Testing and Diagnosis for Autism Spectrum Disorder.
