Many scientists are of the opinion that genetic and environmental factors are the underlying causes of autism spectrum disorder. However, a new study focuses the blame primarily on environmental factors such as pesticide exposure; thus, the studies are particularly relevant to Californians because of the state’s large agricultural areas. The findings were published on March 13 in the journal PLOS Computational Biology by researchers at the University of Chicago and Stanford University.
For the study, the researchers reviewed medical records from more than 100 million Americans. Their investigation revealed that autism and intellectual disability rates correlated at the county level with incidences of genital malformations in newborn males. They note that this association is an indicator of exposure to harmful environmental factors during intrauterine development. They explain that during pregnancy there are certain sensitive periods where the fetus is very vulnerable to a range of small molecules, such as plasticizers, prescription drugs, and environmental pesticides; some of these small molecules are capable of altering normal development. The reason why this occurs; however, it is an experimental observation, especially in boys and especially in the reproductive system. Autism spectrum disorders are approximately five times more common in boys.
The investigators reviewed data from insurance claims that comprised more than a third of the US population. They examined data from individual states and more than 3,100 counties; they compared autism rates and cases of congenital malformations of the male reproductive system, such as micropenis (unusually small penis), hypospadias (urinary outlet on the underside of the penis), undescended testicles. In addition, they studied congenital malformations in the female population. After adjusting for gender, ethnic, socioeconomic, and geopolitical factors, they found that autism rates increased by 283% for every 1 percent increase in frequency of congenital malformations. Furthermore, intellectual disability rates increased by 94% for every 1 percent increase. The association was much stronger in boys because male children with autism were almost six times more likely to have congenital malformations. The incidence of autism in females was also linked with increased malformation rates; however, the association was much weaker.
The authors concluded that congenital malformations very strongly predict the rates of autism, and the rate of malformation per person varies significantly across the nation. Some counties have low rates and some have very high; however, the rate of congenital malformations is higher in counties with higher rates of autism. They noted that the take home message was that the environment may play a very significant role in autism; thus, we should be paying much more attention to environmental factors. The note that this study indicates that research should decrease the emphasis on genetic factors and focus on environmental factors.
Approximately 1 in 88 children suffer from an autism spectrum disorder, according to estimates from the Centers for Disease Control and Prevention (CDC'). The disorder occurs among all racial, ethnic, and socioeconomic groups.