What does emerging evidence suggest about sporadic ASD and twin studies?

• A. They show that genetics have no effect on ASD.
• B. They provide evidence for environmental risk factors of ASD.
• C. They confirm the exclusive role of environmental factors.
• D. They suggest a biological cause for all ASD cases.

Answer: (B)

Emerging evidence from twin studies and research on sporadic autism spectrum disorder (ASD) indicates that environmental risk factors contribute to the development of ASD. Twin studies are particularly informative because they allow researchers to compare the incidence of ASD in identical twins, who share nearly all of their genetics, with that in fraternal twins, who share only about 50% of their genetic information. The findings often reveal that that while genetic factors play a significant role, the presence of ASD in one twin does not always guarantee that the other twin will also have the condition. This discrepancy points towards the influence of non-genetic, or environmental factors that may include prenatal exposures, maternal health, and other social or ecological factors. Therefore, the connection drawn from these studies supports the notion that environmental variables are significant contributors alongside genetics in understanding the etiology of ASD.