Data analysis from previous studies reveals if one twin is on the autism spectrum, there is a 96% chance the other twin will also be diagnosed with ASD. However, symptom severity varies greatly between the twins. Researchers estimate genetic factors contribute to only 9% of the cause of trait variation.
The delivery method of twins may play a role in their neuropsychological development. A correlation has been discovered between twins born by cesarean section and poor cognitive development compared to twins born via virginal delivery.
According to a new study, on average, the variation for human traits and diseases is 49 per cent genetic and 51 per cent due to environmental factors.