Environmental Contributions to Autism: Explaining the Rise in Incidence of Autistic Spectrum Disorders

The incidence of autism spectrum disorders, a heterogenous group of neurodevelopmental disorders is increasing. In response,\udthere has been a concerted effort by researchers to identify environmental risk factors that explain the epidemiological changes\udseen with autism. Advanced parental age, maternal migrant status, maternal gestational stress, pregnancy and birth complications,\udmaternal obesity and gestational diabetes, maternal vitamin D deficiency, use of antidepressants during gestation and exposure\udto organochlorine pesticides during pregnancy are all associated with an increased risk of autism. Folic acid use prior to pregnancy\udmay reduce the risk of autism. Exposure to antenatal ultrasonography, maternal gestational cigarette and alcohol use do not\udappear to influence the risk of autism in offspring. There is little evidence that exposure to environmental toxins such as thimerosal,\udpolybrominated diphenyl ethers and di-(2-ethylhexyl) phthalate in early childhood increases the risk of autism. Apart from birth\udcomplications, the current evidence suggests that the majority of environmental factors increasing the risk of autism occur in the\udantenatal period. Consistent with the rise in incidence in autism, some of these environmental factors are now more common in\uddeveloped nations. Further research is required to determine how these environmental exposures translate to an increased risk of\udautism. Understanding how these exposures alter neurodevelopment in autistic children may inform both the aetiopathogenesis and\udthe strategies for prevention of autism