Environmental Toxins Cause ADHD? Not So Fast.


In a Pediatrics study released earlier this year, scientists from the Harvard School of Public Health found that children who were exposed to higher levels of common pesticides (used on fruits and vegetables) were more likely to have a diagnosis of ADHD.

Children with the highest levels of the pesticide in their system were 93 percent more likely to be diagnosed with the disorder than children with undetectable levels. The chemicals were “organophosphates”—a class of compounds widely used in agriculture.

Studies like these put a sharper focus on possible environmental triggers for attention deficit disorder. In this week’s Science of Kids column, I talk about some of this new data and try to put questions of nature and nurture in perspective.

How big a role do genes play in ADHD?  Scientists have actually put a number on it.The best estimates say the “heritability” of the disorder is 76 percent.  That means that 76 percent of the variance in ADHD is due to genetics. It’s a high number for a psychiatric condition. Depression is estimated at 50 percent (although some studies say that depression in men is less genetically determined).

It’s unnerving, especially as parents, when we hear studies like these about environmental toxins and ADHD, but the picture is rarely as simple as it seems from a headline.  Check out the full article “Could Pesticides Cause ADHD”. There’s also a link to an article on the “Dirty Dozen”—the fruits and veggies most likely to retain pesticides.

Image: Flickr/Muffet