Environmental factors and Autism Spectrum Disorder

Multiple observations indicate that environmental and epigenetic factors play an important role in the emergence of Autism Spectrum Disorder (ASD). Growing ASD incidence rates, the incomplete penetrance of many rare variants linked to autism, and the increased exposure to environmental contaminants, all strongly support the role of Gene x Environment interactions in a substantial fraction of autistic patients. Within this framework, genetically susceptible individuals exposed to detrimental environmental factors at critical times during neurodevelopment, might undergo disrupted brain morphogenesis, neuronal connectivity, and synaptic functioning consequently yielding ASD. Several teratogenic drugs and prenatal viral infections are able to cause autism in humans, as supported by case reports, cohort studies and animal models. Moreover recent studies are showing that some newly identified potential neurotoxicants may negatively affect developmental trajectories, leading to altered cognitive, attentive, behavioral and motor performance, as well as to systemic abnormalities frequently seen in autistic individuals. A variety of mechanisms is potentially involved, ranging from oxidative and inflammatory brain damage to altered gene expression and impaired signal transduction. More research is needed to thoroughly investigate the effects of these compounds on neurodevelopment, to validate their involvement specifically in ASD, to study Gene x Environment interactions in potentially susceptible individuals and to plan targeted prevention strategies.