Alaska Regional Hospital - September 04, 2018

Study links mothers’ pesticide levels with autism in children

For years, scientists have been trying to understand autism spectrum disorders and the causes behind it.

Findings in a new study, published by The American Journal of Psychiatry (2018), state that elevated levels of DDE in pregnant women are associated with an increased risk of autism among their children. The Centers for Disease Control and Prevention defines DDE (dichlorodiphenyldichloroethylene) as the breakdown product of the pesticide DDT (dichlorodiphenyltrichloroethane); an insecticide used in agriculture that was banned in the United States in 1972, but can still be found in the food chain.

According to, the new study evaluated levels of DDE in maternal serum samples drawn from more than 750 children with autism and matched control subjects from a national birth cohort study, the Finnish Prenatal Study of Autism. The odds of autism among children were significantly increased in mothers whose DDE levels were elevated (defined as the 75th percentile or greater). In addition, the odds of children having autism with intellectual disability were increased more than twofold with maternal DDE levels above this threshold. While these results indicate an association, they do not prove causation, although the findings persisted after controlling for confounding factors.

Authors of this study conclude that their findings “provide the first biomarker-based evidence that maternal exposure to insecticides is associated with autism among offspring.”

This study comes four years after research published in The New England Journal of Medicine (2014) added mounting evidence that autism could begin as early as the second trimester of pregnancy.

Researchers from the Allen Institute for Brain Science in Seattle and the University of California, San Diego School of Medicine examined samples of brain tissue from 22 children who died, half of whom had been diagnosed with autism. The scientists found that 10 out of 11 children with autism showed patches of disrupted development in the neocortex, the region of the brain that controls comprehension, reasoning and language.

During the second trimester of pregnancy the cortex normally develops into six distinct layers, each made up of its own specialized brain cells. But in children with autism, the researchers saw patches in which the layers appeared jumbled and disorganized, or where certain cells were missing. Most of these patches were concentrated in areas of the brain that handle functions that are impaired by autism, such as language and understanding social cues.

Future treatment

Autism has no cure, but some children appear to improve as they get older, and early intervention with behavioral and speech therapies can help. The 2014 study could explain why. Because the researchers found the disorganized layers only in patches of the cortex, as opposed to covering the entire brain, they believe that the normal-appearing parts may be able to rewire themselves to take over for the affected patches. Still, much is unknown. The hope is that future studies will point to therapies that can help with that process.


Disclaimer: Content is reviewed regularly and is updated when new and relevant evidence is made available. This information is neither intended nor implied to be a substitute for professional medical advice. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with questions regarding a medical condition.