Certain forms of autism have an entirely genetic origin. This is the case with Fragile X syndrome, Angelman syndrome, and Rett syndrome. These purely genetic syndromes are not the focus of this page.

In general, a genetic predisposition appears to be linked to the development of autism spectrum disorders, as suggested by the following research findings:

    1. The prevalence of autism in the general population appears to be approximately 1%.

    2. In families where one child is autistic, siblings have a 10% chance of also being diagnosed. This percentage rises to 20% when language delay is included.
      Reference: Sibling Recurrence and the Genetic Epidemiology of Autism, Constantino, Zhang, Frazier et al. Am J Psychiatry 2010; 167, 1349-1356

    3. In families where one fraternal (dizygotic) twin is autistic, the other has a 20% chance of also being diagnosed. This percentage increases when bipolar disorders are taken into account

    4. In families where one identical (monozygotic) twin is autistic, the other has about a 90% chance of also being diagnosed.

      Reference : Rosenberg, Law, Yenokyan et al. Arch Pediatr Adolesc Med. 2009;163(10):907-914

    5. Finally, a 2014 Swedish study found inherited genetic anomalies in 52% of cases within a cohort of individuals with autism, with fewer than 3% involving de novo mutations.

      Reference : Gaugler, T., Klei, L., Sanders, S. et al. Most genetic risk for autism resides with common variation. Nat Genet 46, 881–885 (2014).

    For families

    While genetics undeniably play a role, they alone cannot account for the rise in prevalence. Environmental factors also have a significant impact. Autism in your family is therefore not an inevitable fate for future generations.

    First conclusion: while it cannot explain the current rise in autism spectrum disorders, genetics does play an important role in their onset.

    In the 2024 study monitoring the All Babies in Southeast Sweden (ABIS) cohort, the authors report a correlation between the emergence of neurodevelopmental disorders and specific configurations of the HLA system, the genetically inherited part of the immune system.
    Reference : Ahrens et al., 2024, Cell 187, 1853–1873 April 11, 2024 Published by Elsevier

    Second conclusion: the link between genetics and autism spectrum disorders appears to involve, at least in part, a vulnerability of the immune system.

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