ADHD in kids linked to pesticide exposure: NOT SO FAST!

Here is one link to a story about this research. There are many more! ADHD in kids linked to pesticide exposure

Once again the popular press gets science wrong. They've created a good headline, but it seems they didn't even read the scientific article that they write about. As a matter of fact, doing a web search on this topic you come up with this article in the first ten hits, "Pesticides: Main Factor For Attention Deficit Hyperactivity Disorder In Children by Maria Rivera. "A brand new analysis of the United States overall health information ties children’s ADHD with contact with widespread inorganic bug sprays applied to fruits and vegetables. Even as the research could hardly demonstrate that pesticides used in farming contribute to childhood studying challenges, specialists said that the study was persuasive...." Not true. Idiotic. But I also found myself fooled by Maria Rivera, if there is such a person. When I wrote a comment on her blog I had to put my email address in. The blog is nothing more than a scam to sell metal water containers and similar products. They used the research to sell products. Lied about the research to sell products! And I foolishly fell for it ..... See, it can happen to anyone! Your reading what you think is something that is anti-corporation, anti-big pharma, pro-environment when in reality your being taken in by someone wanting to make money from you. (This is very similar to individuals who were taken in by the former medical doctor Andrew Wakefield and his anti-vaccine research which turned out to be nothing more than a means to sell HIS vaccine! The problem is some people,even when the evidence is presented, can't change their minds. They are so committed to something they are blinded to facts.)

The truth about this study (published in the Journal of Paediatrics) is that it is a very good study. Well done. And the results should be taken seriously. They used a structured interview with parents, did a cross sectional study of 1139 children and found 119 children who meet the criterion for ADHD. Adjusting for a number of factors they found higher concentrates of this specific pesticides in urine samples from these children. This is what they got: For children with higher doses of one of the most commonly detected metabolites of DMAP, those children were twice as likely to be the children with ADHD. (They compared those with and without ADHD. The pesticide marker predicted the child would have ADHD at twice the rate it would predict for a non-ADHD child.)

But this is a correlational study only. It CANNOT be used to conclude cause and effect. The authors of the study say that. Anyone familiar with scientific methods would know that (like a science writer for a newspaper or television).

but there are a couple of other concerns. The prevalence rate of children found just to have ADHD in this study was 12%. That's twice what we usually see. Why is that? This, and some other minor problems could mean there is some hidden (not just from us but from the researchers as well) bias in the selection of children for the study.

There is also the question of plausibility. Something basic you always ask when you read scientific research. Yes, organophosphates are neurotoxins. They do have an effect on memory and attention. But toxicity is usually, almost always, related to dose. Are these children really being exposed to a dose that would have an effect? And ADHD has been show over and over again to be related to genetics. How does all this long history of research fit together with these claims ....ooops. Correlations? Of course there may, and I expect are, multiple causes of ADHD, so it may all fit together very nicely. And there are many other plausible causes. MAybe these kids, with higher levels, respond to and metabolize these toxins differently because they have ADHD. It's possible. Maybe something genetic is a factor we just aren't aware of. Maybe this is an outlier, a result outside the norm. That's why scientific experiments need to be replicated several times. Maybe there is something about where these kids got their food, where they are from, where they play. We just aren't sure.

Another example of the problematic thinking going on can be understood from this example: In 1993 a study found that breast-fed children had higher IQs than those who were not breast-fed. Everyone tried to figure out what the ingredient was in the breast milk that made those kids smarter! Those moms who didn't breast feed felt guilty. But after a while researchers began to question some of these assumptions (after-the-fact reasoning or "post hoc, ergo proper hoc" or "this came first, then this, therefore....") There were many other possible causes of they IQ increases. Maybe the mothers who breast fed spent more time with their children, maybe there was a difference in the quality of their interactions. As most scientist know, two events following each other in sequence does not mean they are CAUSALLY related." Correlation does not mean causation. But it does mean that further investigation is called for.

Feed your kids clean food. Avoid pesticides when ou can, as much as you can. Want to eat organic, go ahead. And maybe this study should keep you concerned about this when your shopping. MAybe SOME kids with ADHD, or who "almost" have ADHD will respond poorly to these substances. We just don't know. But as the authors of this study say, this is serious and needs MORE study.

What I do know, for sure and absolutely, is this study does not say in any way shape or form that pesticides are a MAIN factor in ADHD. And we all too easily slip down that slope. I just wish we could expect more from the mainstream press.

You can also find information about my practice at or by downloading this pdf file (click here). My main web site can be found at
Posted on July 1, 2010 .