New Research: Pesticides Associated with Autism

New research may help solve the mystery of autism.

Posted Oct 12, 2018

New research, recently published in the American Journal of Psychiatry, found a significant correlation between autism and pesticides.  The specific pesticide studied was dichlorodiphenyltrichloroethane known as DDT.  It was already widely believed to be toxic, especially as an endocrine disruptor and carcinogen. 

Autism is a neurodevelopmental disorder that affects 1 in 59 children in the United States.  Although the cause of autism spectrum disorder is unknown, it is suspected that autism is caused by a complex interaction between various genes and the environment.  Determining these environmental factors has proved elusive so far. 

A link between autism and environmental toxins has been suspected, and there is growing evidence to support this theory.  However, this is the first study to provide biomarker-based evidence that maternal exposure to pesticides is associated with autism among offspring. 

One of the more notorious pesticides is DDT.  By 1945, it was used widely in the United States and other countries in homes and agriculture.  But due to safety concerns, it was banned in the U.S.  However, stopping the use of this chemical has only limited effect on the potential detrimental consequences of DDT as this chemical takes decades to break down in the environment and accumulates in the fatty tissue in organisms.  This chemical still, to this day, lingers in our tissues and blood.  DDT can also cross the placenta, making it possible that a buildup of residual DDT in a mother can affect her unborn child. 

In this new study, the blood specimens from mothers in early pregnancy were evaluated for the presence of the DDT metabolite known as p, p’-DDE.  The results showed that the odds of a child having autism were increased by a third when levels of p, p’-DDE in the mother’s blood were in the highest 75th percentile, even after confounding factors were taken into account.  Furthermore, the odds of autism with intellectual disability were increased more than two-fold when the blood levels were above this threshold. 

This study proves a correlation of pesticides with autism, but it does not prove causality.  The study needs to be replicated as it will likely have important societal implications.  Understanding the role of pesticides in autism may help us come up with prevention programs, ways to remove DDT from our bodies, and cause us to be more careful in regards to the chemicals we put into our environment. 

References

Brown AS, et al.  Association of maternal insecticide levels with autism in offspring from a national birth cohort.  American Journal of Psychiatry.  2018 Aug 16