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Autism is caused by a combination of genetic and environmental factors. No single cause has been identified and vaccines do not cause autism. This guide explains what current research tells us about the causes of autism.
Autism is caused by a combination of genetic and environmental factors. No single cause has been identified and it is likely that autism in different individuals arises through different combinations of contributing factors. Genetics is the most significant contributing factor: twin and family studies show that autism is highly heritable. At the same time, the same genetic profile does not always produce autism, suggesting that other factors also play a role. The exact mechanisms by which genes and environment interact to produce autism are an active area of research.
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Twin studies have consistently shown autism to be highly heritable. Studies estimate heritability at between 64 and 91 percent. Hundreds of genes have been associated with autism risk through large-scale genomic studies. Rather than a single autism gene, risk is distributed across many genes each contributing a small effect. Some autism-associated variants are inherited from parents; others arise as new mutations in the child.
A significant proportion of autism-associated genetic variants are de novo: they arise as new mutations in the child rather than being inherited from either parent. De novo mutations are found more commonly in autistic people with intellectual disability. The rate of de novo mutations increases with paternal age, which may partly explain the modest association between advanced paternal age and autism risk.
Epidemiological research has identified several prenatal factors associated with modestly increased autism risk, including advanced maternal or paternal age, prenatal exposure to certain medications including valproate, premature birth, complications during pregnancy or birth and prenatal exposure to air pollution. These factors do not cause autism on their own but may interact with genetic vulnerability.
Research into the neuroscience of autism has identified differences in brain development and connectivity present from early fetal development. Autistic brains show differences in the development and organisation of neural circuits involved in social cognition, sensory processing and executive function. These differences reflect the early onset of autism and correspond to the diversity of autism presentation.
Vaccines have been exhaustively studied in millions of children and do not cause autism: the fraudulent 1998 study claiming a link has been thoroughly discredited and retracted. Autism is not caused by poor parenting or emotional neglect: the previously held theory of the refrigerator mother as a cause of autism has been completely disproved. Autism is not caused by screen time, diet or any other lifestyle factor that has been studied.
Understanding the causes of autism helps families reduce feelings of guilt and blame, informs research into early identification and support and helps dispel harmful myths. However, understanding causes should not lead to conclusions about preventing or eliminating autism: many autistic people argue strongly that autism is a natural form of human neurological diversity that deserves acceptance and accommodation.
For related information see our articles on Autism and Genetics and Autism Explained.
There is no single cause of autism. Genetics is the most significant contributing factor, with twin studies showing high heritability. Many genes each contribute a small amount of risk. Some autism-associated genetic variants arise as new mutations in the child rather than being inherited. Prenatal environmental factors may also play a modest role.
Certain prenatal factors have been associated with modestly increased autism risk in epidemiological studies. These associations do not mean those factors cause autism directly: most pregnancies with these risk factors do not result in an autistic child. The genetic contribution to autism risk is substantially larger than any identified prenatal environmental factor.
No. The refrigerator mother theory, which blamed cold or emotionally unresponsive parenting for causing autism, has been thoroughly disproved. Autism is a neurodevelopmental condition with a strong genetic basis. Parenting style does not cause autism.
Visit our Understanding Autism hub for more guides on signs, diagnosis, causes, sensory needs, masking and co-occurring conditions.
The information in this article is provided for educational purposes only and is not intended as medical advice. If you have concerns about autism or any neurodevelopmental condition, speak to a qualified healthcare professional. SENDhelp Education Limited accepts no responsibility or liability for any loss or damage arising from reliance on this content. Any links to third-party websites are provided for convenience only and do not constitute endorsement of their content.
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