Can lead exposure cause ADHD?

I have done a great deal of research on lead toxicity and noticed that many of the symptoms of high lead levels are similar to symptoms of ADHD. Has there been any research done on possible correlation, and are doctors screening these kids for lead before labeling them as having ADHD?

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Robert Steele

Robert W. Steele, MD, is a board certified pediatrician at St. John's Regional Health Center in Springfield, MO. He graduated from medical... Read more

Dear Sheila,

You have asked an outstanding and thoughtful question because it certainly is true that many of the symptoms of lead toxicity and ADHD are similar. But while investigating a correlation between the two may seem like an obvious thing to do, there actually have not been a whole lot of studies done to fully answer this question. Most of the studies that have been done were published only in the last 6-7 years, and they have given conflicting results.

As you know, agreement upon how high a lead level needs to be to cause significant symptoms is rather controversial. The most conservative findings about when lead toxicity could occur is when the lead level is as low as 10. And while most researchers and pediatricians agree that medical intervention should occur in any child who has a level >25, there is still disagreement around the country about what to do about the child whose level is 10-24. The Center for Disease Control has nicely outlined this controversy and included their recommendations. But your question has more elusive implications.

If we can detect subtle but significant neurologic and psychological differences in children with lead levels as low as 10, could there be an effect lead is causing at levels lower than this? In other words, could ADHD be caused by lead levels currently thought to not be problematic? The answer is nobody knows for sure. The few studies which have been done are conflicting, but even the ones which do implicate lead as a possible cause, do not advocate intervening with medications to lower the lead level. Rather, they emphasize more awareness among health professionals as well as the public to understand what environments are at high risk for lead exposure so that those areas where lead exists can be eliminated or avoided. Therefore, routine lead levels prior to diagnosis of ADHD are generally not done.

Sheila, the association between ADHD and lead if it exists at all is unknown. Certainly, more studies need to be done to answer this question. If you continue in your research about lead over the next few years, you may run across some new ones that will hopefully give us an result either way. The number of children currently identified with ADHD is so much larger than those with lead toxicity that I suspect if any link exists, it is probably only a contributing factor rather than a direct cause. But the researchers may prove me wrong, so we will both have to keep our eyes open for new developments.

Good luck to you.

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