A new-old theory about the cause of attention deficit hyperactivity disorder (ADHD) is crawling across the nation: pesticides.
In the journal Environmental Health a group of American authors examined the relationship between a common pesticide, pyrethroid, and ADHD. They used clinical information and urine samples from hundreds of kids collected as part of a 2001-2002 National Health and Nutrition Examination Survey (NHANES)—a periodic survey that’s at the center of countless other studies of American health and disease.
The authors asked a simple question: Are kids with ADHD more likely to have detectable levels of pyrethroid (or its chemical metabolites) in the urine versus kids without ADHD? The answer, is short, was yes. They found that kids with detectable pyrethroid were twice as likely to have ADHD as kids without; furthermore, and perhaps more convincing, the higher the level of pyrethroid, the greater the likelihood of ADHD.
That clinches it, right? Of course not. Simple things are never simple—and ADHD is nothing if not incredibly dense.
There are many uncertainties raised about the study that the researchers acknowledge, such as that a different group performed a similar analysis and did not find the association. Or that the urine samples were a single level taken once per kid and therefore did not reflect overall exposure. Even more perplexing, since the samples came from a time before pyrethroid’s widespread use as an insecticide, why did the ADHD kids have levels in their urine? There shouldn’t have so much of it around the environment.
All of these sorts of concerns circle around the larger question: Is there something behaviorally different about the families of kids with ADHD or their families that makes them more likely to have detectable urine pyrethroid levels?
Perhaps they are really, really afraid of bugs, and cope by obsessively spraying and calling Orkin twice a month to boot. Maybe such bug-o-phobia is more common in people with ADHD or their parents. Maybe people with ADHD are more likely to lick sprayed surfaces as part of the overall collection of symptoms that constitutes ADHD. Maybe, maybe, maybe.
The point is this—ADHD, like autism and cancer and many other common conditions that touch so many people, is really complex. There are plausible theories supporting the notion that genetics plays a heavy role in its development; similarly that premature birth or head trauma is important; or that bad diets are the issue; or types of allergies; or perhaps infections with strep and various viruses that trigger a cascade of unfortunate events. Or maybe it is the fault of schools or bad friends or the insatiable urge of psychiatrists to give every human on the planet a diagnosis of one type of another.
A simple rule of thumb is this: The more plausible theories there are about what causes a disease, the more confused experts remain. Cigarettes and lung cancer is a classic case of cause and effect. No one outside of Big Tobacco disputes it. Yes, there are very important genetic and other contributors, but no one questions the major driver.
But the list of conditions for which we have nailed down a specific cause (obesity and type 2 diabetes, for example) remains disappointingly brief. So off we go in hot pursuit of the big clue for additional diseases. Right now, we are in a moment of gene fetishism where every problem is being traced to a faulty snippet of DNA. It is the auto-repair-shop view of disease where all misery will be prevented with a simple clip, splice, and solder approach.
Or for those not part of the Genes ‘R’ Me generation, perhaps there is relief to be found in the Paleo diet, a back-to-caveman ethos that removes any trace of deforming modernity from a person’s reach. Or maybe it is a problem with self-esteem—the sort of thing Dr. Phil can solve by a blunt aphorism. Indeed the pursuit of a single unifying explanation for ADHD seems much like the condition itself— frantic, contrary, scattered, and exhausting to follow.
This Officer Krupke view of human frailty is actually fine for the most part. Sifting through possible explanations is pretty much the full-time occupation of every sentient soul; and of course parents want answers when their children are struggling or ill.
The problem though is that this too often sets up a promise of a simple “cure” —i.e., “no more bug spray and my problems are solved!” Or worse, it establishes the converse of the cure—self-blame: “If only I hadn’t bought that bug spray, my kid wouldn’t have ADHD.”
Too often, half-baked explanations result in full-bore regret and reproach, something far more corrosive to individuals and to families than any bug spray ever was.