You will often hear people say that autism is genetic.
That is a reasonable summary, but the real story is much more interesting than the idea that scientists have discovered an “autism gene”.
They haven’t.
What research increasingly shows us is that genetics plays a major role in autism, but there is no single genetic difference shared by every Autistic person. Instead, many different genetic variations can contribute to the development of an Autistic brain.
This helps explain something Autistic people and families already know very well: there is enormous variation between Autistic people.
Understanding what scientists actually mean when they say autism is “genetic” can also help us move away from some of the myths that have surrounded autism for decades.
One of the strongest indications that genetics is involved in autism is that autism tends to run in families.
If one person in a family is Autistic, there is a greater chance that other members of that family will also be Autistic or have related traits.
Sometimes this becomes particularly obvious after a child is identified as Autistic.
Parents begin learning about autism because they want to understand their child and suddenly start recognising familiar traits elsewhere in the family.
A parent might think:
“I did exactly that when I was a child.”
Or:
“That’s just like their grandfather.”
Someone who always thought they were simply very sensitive to noise, extremely particular about routines, deeply focused on certain interests or exhausted by social situations may begin to understand those experiences differently.
This doesn’t mean every relative of an Autistic person will be Autistic.
It simply reflects the fact that genetics is an important part of the picture.
Twin studies have been particularly useful in helping researchers understand the role genetics plays in autism.
Identical twins share almost all of their DNA, while non-identical twins share considerably less.
Researchers have found that when one identical twin is Autistic, the other twin is much more likely to also be Autistic than would be expected by chance.
Studies involving siblings and wider families show similar patterns.
This does not mean genetics determines every detail of an Autistic person’s life or development. It does tell us that genetic differences make a substantial contribution to whether someone is Autistic.
This is where things become particularly interesting.
For many years, people imagined that scientists might eventually discover a particular gene responsible for autism.
That hasn’t happened.
There is no single autism gene.
Instead, researchers have identified many genetic variants associated with autism, and our understanding of these continues to develop.
For many Autistic people, it appears to be the combined influence of many genetic differences rather than one individual gene that matters.
Some variants are relatively common and may individually have only a tiny effect. Others are much rarer and can have a larger effect on development.
Different Autistic people can therefore have very different genetic profiles.
This makes sense when we think about how diverse Autistic people actually are.
Two people can both be Autistic and still have completely different personalities, abilities, difficulties, sensory experiences, communication styles and support needs.
One person might speak very little or communicate using AAC.
Another might be extremely verbal.
One person may need substantial support with everyday living.
Another may live independently but struggle significantly with sensory overload, executive functioning or burnout.
Some people have intellectual disabilities.
Many do not.
Some people are also ADHD.
Some are not.
Some have epilepsy or other medical conditions.
Others don’t.
Autism isn’t one identical experience repeated across millions of people, so it should perhaps not be surprising that there isn’t one simple genetic explanation either.
When people hear that something is genetic, they sometimes assume that means it must have been directly inherited from a parent.
Genetics is more complicated than that.
Some genetic variations are inherited from our parents.
Others can arise spontaneously during the formation of an egg or sperm, or very early in development. These are often referred to as new or “de novo” genetic variants.
So an Autistic child can have genetic differences associated with their development even when those particular differences are not found in either parent.
In other families, Autistic traits can appear across several generations.
There is no single pattern that explains every Autistic person.
It is also important to understand what researchers mean when they talk about genetic influence.
Genes contribute to how our brains and bodies develop, but development is an incredibly complicated process.
Thousands of genes are active at different stages of development and interact with each other and with biological and environmental factors.
This means we should be careful with simple statements such as:
“Gene X causes autism.”
For some rare genetic conditions or variants, there may be a strong association with autism or particular developmental differences.
But for autism more broadly, the picture is much more complex.
Genetics can strongly influence development without providing a simple blueprint that predicts exactly what an individual person will be like.
People sometimes ask how autism can be genetic when Autistic people can be so different.
The genetic complexity actually helps us understand why.
There are many possible combinations of genetic variation.
On top of that, every Autistic person has the rest of their genetic makeup too.
An Autistic person doesn’t just have “autism genes”. They have genes influencing height, appearance, temperament, memory, attention, movement and countless other aspects of being human.
Then there is everything that happens throughout life.
Education, relationships, culture, opportunities, trauma, health, acceptance, discrimination and the environment someone grows up in can all shape their experiences.
Being Autistic is one part of a whole human being.
This is why knowing that somebody is Autistic tells you something important about them, but it doesn’t tell you everything about who they are.
Even within one family, autism can look very different.
One family member might have been identified in early childhood because their differences were immediately noticeable.
Another might not realise they are Autistic until adulthood.
Someone may have significant communication support needs, while another family member is highly verbal.
One person may struggle with noise while another seeks out particular sounds.
One may love routine while another appears much more spontaneous but struggles with unexpected changes in less obvious ways.
This can sometimes make people question whether two relatives can really both be Autistic.
They can.
Sharing a neurotype does not mean having identical needs or personalities.
When scientists use the word “environment”, it can easily be misunderstood.
People sometimes hear “environmental factors” and assume researchers mean parenting, food, television, phones or something parents did during childhood.
That isn’t what the term necessarily means in scientific research.
In this context, environment can refer very broadly to influences that are not explained simply by inherited DNA.
Researchers continue to study how genetics, biology and development interact.
What is important is not to turn uncertainty into an opportunity for unsupported claims.
Whenever there is something science does not completely understand, somebody will usually appear offering a very simple explanation.
Autism has attracted a lot of these explanations over the years.
One of the most persistent autism myths is the claim that vaccines cause autism.
They don’t.
The claim has been investigated extensively and large studies have not found evidence that vaccination causes autism.
The original paper that helped popularise fears about the MMR vaccine and autism was eventually retracted, but unfortunately the idea had already spread widely.
Decades later, families still encounter versions of the same claim online.
This matters because misinformation about autism doesn’t only affect vaccination decisions. It also affects how people think about Autistic people.
If autism is presented as something that suddenly happened to a previously “normal” child because of an outside event, the natural response is to search for something that will reverse it.
That has helped create a market for supposed autism cures, detoxes and other interventions.
Autistic children deserve better than being subjected to treatments based on fear and misinformation.
Parents do not make their children Autistic.
It sounds obvious today, but historically parents, and particularly mothers, were blamed for autism.
The notorious “refrigerator mother” theory suggested that autism resulted from emotionally cold parenting.
It was wrong.
It also caused enormous harm to families.
We now understand far more about the biological and genetic contribution to autism.
Parenting can obviously influence any child’s experiences, confidence, relationships and wellbeing. A supportive environment matters enormously.
But parenting does not create autism.
Screen time is another subject that periodically becomes attached to autism discussions.
Excessive screen use can affect sleep, activity, opportunities for interaction and other aspects of any child’s life.
That is a completely different claim from saying screens cause autism.
They don’t turn a non-Autistic brain into an Autistic one.
If parents are concerned about their child’s development, they deserve useful information and appropriate support rather than blame.
There is also no evidence that a particular everyday food or diet is the underlying cause of autism.
Autistic people can absolutely have food-related difficulties.
Sensory differences can affect which textures, tastes, smells and temperatures someone can tolerate.
Some Autistic people have gastrointestinal conditions, allergies or other medical issues that require appropriate investigation and treatment.
Those problems should be taken seriously.
But treating a genuine gastrointestinal problem is not the same thing as treating autism.
Autistic people deserve proper medical care without every health problem being presented as the hidden “cause” of their autism.
For much of autism’s modern history, autism has been framed primarily as something that went wrong.
Once you begin from that position, the obvious next question is:
“What caused it?”
And after that:
“How do we prevent or cure it?”
But there is another way to think about the question.
Autistic people have existed throughout human history, even though the language and diagnostic categories used to describe us are relatively recent.
Human brains vary.
People vary in communication, attention, sensory processing, social interaction, movement, interests and ways of thinking.
Some of those differences can create significant disability, particularly when someone’s needs are not accommodated. Some Autistic people require substantial lifelong support and those needs should never be minimised.
Recognising autism as part of human neurological diversity does not require us to pretend that nobody struggles.
Acceptance and support are not opposites.
We can accept an Autistic person completely while also recognising where they need help.
As genetic research develops, there are important ethical questions to consider too.
Scientific knowledge is not automatically good or bad. What matters is how we use it.
Genetic research may help us understand development, identify medical conditions that occur alongside autism and provide better healthcare and support.
But Autistic people also have understandable concerns about research that focuses primarily on preventing Autistic people from existing rather than improving the lives of Autistic people who are already here.
That distinction matters.
If genetics helps a doctor recognise that an Autistic child has an increased risk of a particular medical condition, that knowledge may be extremely useful.
If genetic research is used primarily to ask how society can have fewer Autistic people, we are having a very different conversation.
Autistic people should be included in discussions about where autism research goes and what its goals should be.
Yes, genetics plays a very significant role in autism.
But that does not mean scientists have discovered a single gene that makes somebody Autistic.
The picture is far more complicated.
Many genetic variants appear to be involved. Different combinations may contribute in different people. Some variants are inherited and others arise newly. Biology and development are complex, and research continues to improve our understanding.
What we can confidently move away from are the old ideas that autism is caused by bad parenting or the modern myths blaming vaccines, screens or particular foods.
Autism is not something a parent accidentally gave their child by making the wrong decision.
And an Autistic child is not a damaged version of the child they were supposed to be.
They are the child who is actually here.
Understanding the genetics of autism should help us understand human variation, improve healthcare and provide better support. It should also remind us how much there still is to learn.
The most useful question isn’t simply why an Autistic person exists.
It is how we can understand them, listen to them and make sure they have what they need to live a safe, healthy and fulfilling life.
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