How do genes and environmental factors interact in autism spectrum disorder?

The exact causes of autism spectrum disorder (ASD) remain unclear, but research indicates that it arises from complex interactions between genes and environmental factors.21

Genetic factors contribute to susceptibility, though the degree of influence varies; for instance, research suggests that environmental factors may play a larger role than genetics in some cases. Genetic vulnerability also appears to be sex-dependent, with the "female protective model" suggesting that females require more mutations than males to develop the condition. Specific genetic variations, such as those involving the CNTNAP2 gene, have been linked to structural and functional differences in the brain, affecting neuronal connectivity.23

Environmental factors, particularly those occurring during pregnancy, also influence development. Maternal infections can trigger immune system activity that may alter fetal brain development. Other associated environmental factors include advanced parental age at conception and the use of certain antidepressants during pregnancy. It is important to note that extensive scientific research has debunked the claim that childhood vaccinations are a cause of autism.2