Do Pesticides Cause ADHD?

Health Writer

What  causes ADHD? The question has been asked for years and yet there are no clear answers. Some scientists believe that while your  genes might make you susceptible to ADHD, the environment might also play a role in who develops ADHD. A recent study looked at whether insecticides, specifically those containing pyrethroid, might contribute to ADHD.

What is Pyrethoid?

Pyrethroid compounds are synthetic versions of pyrethrum. This comes from dried and crushed flowerheads of chrysanthemums. Although this is an effective insecticide, with low toxicity to people, it is also expensive and therefore not always useful in farming and other applications, including households.

In the late 1940's, scientists discovered how to synthesize pyrethrum and by the 1960s, there were a number of different versions of this synthesized compound, used in household and commercial insecticides. Scientists continue to work to improve the insecticides and many now are quite different than the original formulas. The ones used today are "more toxic to insects and last longer in the environment than the early compounds" according to the website  Texas A&M AgriLife Extension.

Today, there are many  different formulations and names  for pyrethroids:

  • Cyphenothrin
  • Esfenvalerate
  • Allethrin
  • Deltamethrin
  • Tralomethrin
  • Bifenthrin
  • Fenpropathrin
  • Cyfluthrin
  • Gamma cyhalothrin
  • Lambda-cyhalothrin
  • Piperonyl butoxide
  • Tau-fluvalinate
  • Permethrin
  • Imiprothrin
  • Sumithrin
  • Tetramethrin
  • Cypermethrin
  • Prallethrin
  • Resmethrin
  • Metofluthrin
  • Tefluthrin

In addition to household insecticides (check the labels for any of the previous names), these compounds are often used on your lawns, in your garden, on golf courses and in other commercial applications.

The Association Between Insecticides and ADHD

In a recent  study, completed at Rutgers University, in conjunction with Emory University, the University of Rochester Medical Center and Wake Forest University, researchers found that mice who were exposed to the pyrethroid pesticide deltamethrin, in utero and through breastfeeding, exhibited ADHD features, such as  hyperactivity, deficits in  working memory, attention deficits andimpulsive behavior. As with people, the researchers found ADHD behaviors more common in male mice than in females. These behaviors continued into adulthood, even when the pesticide was no longer in their system.

The report issued by  Rutgers University  states, "These finding provide strong evidence...that exposure to pyrethroid pesticides...may be a risk factor for ADHD." James, Richardson, lead    author of the study, further states, "Although we can't change genetic susceptibility to ADHD, there may be modifiable environmental factors, including exposures to pesticides that  we should be examining in more detail...We need to make sure these pesticides are being used correctly and not unduly expose those who may be at higher risk."

The scientists also looked at medical data from the Centers for Disease Control, National Health and Nutrition Examination Survey. Both the answers to questions such as whether a child had been diagnosed with ADHD and urine samples were reviewed. According to the researchers, children with higher levels of pyrethroid pesticides in their urine were twice as likely to have been diagnosed with ADHD.

Pregnant women, those nursing and young children might be more susceptible to exposure to these types of pesticide "because their bodies do not metabolize the chemicals as quickly." Richardson suggests that additional studies be conducted to find out how these chemicals affect fetuses and young children.