August, 2019

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Largest Study to Date Finds Autism Is Mostly Heritable

By Chelsea Toledo, M.A. on August 15, 2019

Background: Autism Spectrum Disorder (ASD) can be caused by multiple risk factors.  Risk factors increase the likelihood of developing a condition and can be genetic or environmental. Genetic risk factors relate to variations in our DNA, while environmental factors stem from social, physical, or chemical exposures and can be present during fetal development or months to years after birth.


What’s New: A recent study set out to determine the nature of the risk factors that were most commonly associated with an ASD diagnosis. The authors analyzed the largest-ever dataset for this purpose – containing medical information for more than 2 million births from five different countries: Denmark, Finland, Sweden, Israel, and Western Australia.


Looking at multiple generations represented within the dataset, the researchers found:


  • In total, 22,156 ASD diagnoses were recorded within the sample (about 1 percent).
  • Overall, more than 80 percent of ASD cases were found to be heritable.
  • Heritability varied by country, ranging from 50.9 percent heritability in Finland to 86.8 percent heritability in Israel.
  • Maternal effects (such as illness during pregnancy) were associated with only about 1 percent of causes.
  • Other environmental risk factors were found to have an additive effect with genetics.

Why it’s important: This is the largest-ever study to suggest that ASD is largely genetic. As this study suggests, environmental factors interact with genetic risk factors and their association with ASD varies by country – a pattern that merits future study.


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