Jojy Cheriyan MD,MPH February 16, 2015

A commonly used pesticide (Pyrethroid) may alter the development of the brain’s dopamine system – responsible for emotional expression and cognitive function – and increase the risk of Attention Deficit Hyperactivity Disorder (ADHD) in children, according to a new Rutgers study.

Pyrethroids are used widely as insecticides both in the home and commercially, and in medicine for the topical treatment of scabies and head lice. In tropical countries mosquito nets are commonly soaked in solutions of deltamethrin as part of anti-malarial strategies. Pyrethrin based anti-dandruff shampoos, pet-care sprays etc, are also widely available in the market. But no studies have been done yet to test if the strength used in these products can cause ADHD. The new Rutgers study will open door for more research.

The research published on January 29,2015, in the Journal of the Federation of American Societies for Experimental Biology (FASEB), by Rutgers scientists and colleagues from Emory University, the University of Rochester Medical Center, and Wake Forest University discovered that mice exposed to the pyrethroid pesticide deltamethrin in utero and through lactation exhibited several features of ADHD, including dysfunctional dopamine signaling in the brain, hyperactivity, working memory, attention deficits and impulsive–like behavior. These findings provide strong evidence, using data from animal models and humans, that exposure to pyrethroid pesticides, including deltamethrin, may be a risk factor for ADHD. Using data from the Centers for Disease Control, National Health and Nutrition Examination Survey (NHANES) the Rutgers scientists analyzed health care questionnaires and urine samples of 2,123 children and adolescents. Researchers asked parents whether a physician had ever diagnosed their child with ADHD and cross-referenced each child’s prescription drug history to determine if any of the most common ADHD medications had been prescribed. Children with higher pyrethroid pesticide metabolite levels in their urine were more than twice as likely to be diagnosed with ADHD.

ADHD is a disorder that mostly affects children, ages 4-17, with boys being affected 3- 4 times more likely than girls. Often diagnosed when the child starts to attend school full time. Strong evidence exists regarding the genetic susceptibility to ADHD, but, no specific gene has been found yet. Moreover, studies have previously hinted at environmental factors, including exposures to pesticides and synthetic chemicals. Young children and pregnant women may be more susceptible to pesticide exposure because their bodies do not metabolize the chemicals as quickly.

More human studies are needed to make conclusive evidence on the role of pyrethroids in causing ADHD.

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