Autism spectrum disorder today: not only genetics.

Today, a significant role of genetic factors is widely accepted also in non-syndromic autism spectrum disorder (ASD), that is ASD not secondary to a well-known genetic condition. Modern genetic techniques, such as microarray and whole-genome sequencing, showed the involvement of a large number of genes in ASD etiopathogenesis. However, the dramatic increase of ASD prevalence during the last decades suggests that environmental factors also play an important role. The pre-, peri-, and postnatal exposure to many heterogeneous environmental factors have been hypothesized to be involved, such as air pollutants, pesticides, and other endocrine-disrupting chemicals. Further research is needed to understand the subtle interactions between genetic and environmental factors in the etiopathogenesis of ASD, considering also the concept of epigenetics, which is a very important gene regulation mechanism based on chemical modifications of DNA and histone proteins, without altering the DNA sequence. Moreover, an increasing amount of literature data suggest that epigenetic mechanisms could be the mediators of effects deriving from environmental factors both in ASD and in other neurodevelopmental disorders.