BEING born a twin may increase the risk of developing autism. Two separate investigations hint that the competitive environment twins experience in the womb helps to trigger the disorder. However, the scientists are still arguing over the significance of the results, which could turn out to be a mirage.
Many studies appear to show that autism is 70 to 90 per cent attributable to genetic factors. This figure comes from comparing how often autism is shared between genetically identical twins compared with fraternal twins, who are no more alike than any other siblings. But that analysis assumes there is no…
