A range of genetic and developmental mechanisms.
Autism · genetics · recent research
What causes autism?
Autism has multiple origins, with a strong genetic contribution. There is no single cause or explanation that applies to every autistic person. [1]
The term Asperger’s syndrome, still used by some people, refers to a former diagnosis now included within autism spectrum disorder (ASD). Current research mainly examines the spectrum as a whole; its findings do not always describe the profiles previously called Asperger’s specifically. [1]
Updated 7 October 2026
Parenting and a lack of affection do not cause autism.
Neither a DNA test nor a brain scan is sufficient to diagnose ASD.
A substantial genetic contribution
A large study across five countries estimated the heritability of ASD at approximately 80%. This describes the proportion of variation in underlying susceptibility attributed to genetic differences in the populations studied. It does not mean that a person’s autism is “80% caused by genes”, or that they have an 80% chance of passing autism on to their children. [2]
Autism can occur more frequently within some families without every relative being autistic. Having no diagnosed relatives does not rule out ASD. [1] [3]
There is no single “autism gene”
Many common genetic variants, each with a small effect, can contribute to susceptibility. Rare variants may have a larger effect: some are inherited, while others arise de novo, without being present in the parents. These mechanisms can combine. [3]
Genetics influences, among other processes, the development and functioning of nerve cells. On its own, it cannot predict a person’s profile, abilities or support needs. [4]
What research from 2025–2026 adds
Different profiles
A study of 5,392 autistic children identified four research groups associated with different genetic and developmental profiles. These are scientific findings, not four new official diagnoses. [4]
Age at diagnosis matters
Another study linked age at diagnosis to different developmental trajectories and polygenic profiles. A later diagnosis therefore does not necessarily have a single explanation. [5]
Studying broader populations
Research published in September 2026 explored the diversity of genetic contributions across ancestries. It highlights the limitations of studies historically focused on people of European ancestry. [6]
Associated factors: separating risk from cause
Parental age, very preterm birth, low birth weight and certain prenatal exposures are associated with a higher likelihood of ASD. These factors are neither necessary nor sufficient to explain an individual’s autism. [1] [7]
An association does not prove causation.
A 2025 study of more than one million children found that many associations between maternal health and autism weakened after accounting for shared family factors. This cautions against simplistic explanations that place blame on parents. [8]
Parenting and vaccines do not cause autism
Parents are not responsible for their child’s autism. A lack of affection or poor parenting does not explain it. A supportive environment can nevertheless promote development and well-being. [11]
Vaccines do not cause autism. The WHO review published in September 2026, covering studies from 2010 to August 2025, confirms that the most rigorous research does not support a causal link. [9]
Understanding causes does not replace an assessment
Diagnosis relies on a comprehensive clinical assessment: developmental history, social communication and interaction, repetitive behaviours, sensory differences, their impact on daily life and other possible explanations. Questionnaires provide clues; they are not sufficient for a diagnosis. [10]
An MRI scan or genetic test cannot, on its own, confirm or rule out ASD. Further medical investigations may be appropriate in certain circumstances, with referral to a suitable professional. [10]
Wondering about your own experiences?
An assessment can help explore the possibility of autism spectrum disorder and provide a clearer understanding of your difficulties, strengths and needs.
The video on this page
The original French-language video has been retained. For recent scientific findings, please refer to the updated text and sources below.
Further reading
Scientific sources and clinical guidance
Selected research and guidance consulted for this update. Recent studies shed light on mechanisms; they do not establish a certain cause for an individual’s autism.
- NIMH — Autism Spectrum Disorder
- Bai et al. (2019) — Genetic and environmental factors, five-country cohort
- Zhou et al. (2022) — Rare inherited and de novo variants in 42,607 autism cases
- Litman et al. (2025) — Phenotypic heterogeneity and genetic programs
- Zhang et al. (2025) — Genetic profiles and age at diagnosis
- Mendes et al. (2026) — Multi-ancestry genetic architecture
- OMS / WHO — Autism: causes and associated factors
- Khachadourian et al. (2025) — Familial confounding and maternal health
- OMS / WHO (2026) — Vaccines, thiomersal and autism: evidence review 2010–2025
- NICE — Autism in adults: assessment and diagnosis (CG142)
- OMS / WHO — Autism: questions and answers
