Autism, ADHD and Other Developmental Impacts

Around 1 in 54 American children are diagnosed with autism spectrum disorder. Boys are 4 times more likely to develop autism.

The pathway from fertilized egg to the day of birth, and life passages through infancy, childhood and adulthood, can be disrupted, delayed, or driven off course in a variety of ways, with widely varying consequences.

Birth defects are one, often unmistakable example of adverse developmental effects, but many others cannot be seen or diagnosed at birth, and may or may not be observable, or apparent to attentive parents until children pass through puberty.

Most recent pesticide-related developmental research has focused primarily on effects that alter or impair the integrity of the neurological, immune, or reproductive systems. Such impacts encompass a broad array of adverse outcomes:

Reduced IQ, behavioral problems, ADHD and autism;
Autoimmune diseases and heightened vulnerability to pathogens, cancer, and other factors that can trigger illness; and
Abnormal sexual development and impaired reproductive ability and inclinations.

In particular, the now proven adverse impacts of certain insecticides on neurological development have received intense focus by scientists worldwide. Such impacts can lead to reduced IQ, as well as a number of behavioral problems and learning disabilities. The extensive literature on this topic is accessible via our bibliography under the tags developmental impacts and neurodevelopmental toxicity.

Prenatal exposure to herbicides has been linked to an increased risk of developmental disorders like autism.

Recent research has also linked herbicides, and in particular glyphosate (aka Roundup), to neurodevelopmental disruptions leading to adverse birth outcomes including autism.

The largest and most sophisticated population-based study of pesticides and autism was published in the British Journal of Medicine in 2019. The von Ehrenstein et al study was conducted by a University of Southern California led team, and reported a 33% elevation in the risk of autism spectrum disorder among children with recognized learning disabilities, compared to matched control children less likely to be exposed to glyphosate from nearby farm applications.

Surprisingly, living near areas where glyphosate-based herbicides were applied was a more significant factor in autism than living near where the organophosphate (OP) insecticides chlorpyrifos, diazinon, and malathion were applied.

For this reason, The Heartland Study protocol includes annual developmental assessments at age 3 and hopefully through age 16 (pending funding), to enable calculation of odds rations linking herbicide exposure levels and autism and other developmental and behavioral outcomes.

To learn more, see these resources:

For a recent review of known research on pesticide exposure, autism and ADHD, see this meta-analysis (Roberts et al., 2019).
This case study by Dr. William Shaw looks at one farm family whose triplets with autism spectrum disorder all showed elevated urinary glyphosate levels (Shaw, 2017).
A team of French scientists found that low-dose pre- and post-natal exposure to glufosinate ammonium herbicide induced autism-like symptoms in mice (Laugeray et al., 2014).

For more on why this all matters, see HHRA Science Advisory Board member Dr. Bruce Lanphear’s article “The Impact of Toxins on the Developing Brain” (Lanphear, 2015). Scientists have tried to estimate the economic impacts of neurodevelopmental deficits caused by endocrine-disrupting chemicals, including many herbicides (Attina et al., 2016).