Study Debunks Autism As Primarily Genetic Disorder

      A rigorous study of nearly 400 twins has shown that environmental factors have been underestimated, and genetics overestimated, for their roles in autism spectrum disorders.
      The study found that the children’s environment represents more than half of the susceptibility — 55 percent in the most severe form of autism and 58 percent in the broad spectrum of the disorder — while genetics is involved in 37 percent and 38 percent of the risk, respectively.
      This is the largest and most rigorous twin study to date to research the genetic component of the disorder, and tapped expertise from the UCSF Institute for Human Genetics and Stanford University — which jointly led the research — as well as from Kaiser Permanente, UC Davis, the Autism Genetic Research Exchange and the California Department of Public Health.

      “Autism had been thought to be the most heritable of all neurodevelopmental disorders, with a few small twin studies suggesting a 90 percent link,” said UCSF geneticist Neil Risch, director of the UCSF Institute for Human Genetics and senior author of the paper. “It turns out the genetic component still plays an important role, but in our study, it was overshadowed by the environmental factors shared by twins.”
      “Our work suggests that the role of environmental factors has been underestimated,” said Dr. Joachim Hallmayer, first author of the paper and an associate professor of psychiatry and behavioral sciences at Stanford University.
      What exactly those environmental factors are, Hallmayer said, is the “multimillion dollar question,” but he noted that the disorder’s manifestation in very young children indicates a cause early in life and possibly during pregnancy.
      Autism spectrum disorder (ASD) is a range of