Identical twins with autism spectrum disorder (ASD) often experience large differences in symptom severity even though they share the same DNA, according to an analysis funded by the National Institutes of Health.
The researchers determined a 96% chance that if one twin has ASD, the other has it, too. However, symptom scores varied greatly between twins diagnosed with ASD. The researchers estimated that genetic factors contributed to only 9% of the cause of trait variation among these twins. In contrast, among pairs of identical twins without ASD, the scores for traits were very similar.
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