• Previous studies of risk for autism spectrum disorders appear to have underestimated the contributions of genetics.
  • Recent analyses indicate that 83-98% of risk is based on genetics.
  • As studies have shown time and time again, it has nothing to do with vaccines.
  • Autism is essentially a genetic disorder.

~ David Baxter

Genetic Factors Account for the Majority of Autism Risk
by Megan Brooks, Medscape
September 27, 2017

A reanalysis of data from a previous study on the familial risk for autism spectrum disorder (ASD) suggests that genetics contributes 83% of the risk for ASD.

The original study, which involved more than 2 million families, suggested that genetics contributes 50% of the risk for ASD. That study was published in JAMA in 2014 and was reported at that time by Medscape Medical News. ....

For their reanalysis, using the underlying data from the original study, Dr Sandin and his coinvestigators utilized an alternate method to calculate the heritability of ASD, with far different results.

The results were published online as a research letter on September 26 in JAMA.

The researchers tested various models. Using the best-fitting model, the ASD heritability in the new analysis was estimated to be 0.83 (95% confidence interval [CI], 0.79 - 0.87). Using only twins, the heritability was estimated to be 0.87 (95% CI, 0.68 - 0.96).

The investigators note that the 83% estimate is "slightly lower" than the roughly 90% estimate reported in earlier twin studies and is higher than the 38% estimate reported in a California twin study, but that the estimate was made with "higher precision." Like earlier twin studies, shared environmental factors contributed minimally to the risk for ASD, they point out.

"The method initially chosen in the previous study led to a lower estimate of heritability of ASD. The current estimate, using traditional methods for defining ASD discordance and concordance, more accurately captures the role of the genetic factors in ASD. However, in both analyses, the heritability of ASD was high and the risk of ASD increased with increasing genetic relatedness," [Dr Sandin and colleagues wrote].
JAMA. Published online September 26, 2017. Abstract