Toxins and Pollutants: Impact on ADHD
Medscape: New studies report an association between prenatal pollution exposure and increased risk for ADHD symptoms and conduct disorder. What is known about potential environmental contributors to ADHD, and do you discuss these with patients?
Dr Lipkin: This is a fascinating area of medical research that we are beginning to delve into. Researchers on the West Coast have been championing this the most when it comes to such developmental disorders as autism and ADHD.
Recent studies have looked at polychlorinated biphenyls (PCBs) and related pollutants and their effect on children's development overall, as well as specifically on the incidence of ADHD. In addition to PCBs, people have looked at water contaminants and air pollutants. We are just starting to see the clues and concerns, but there are still no absolute conclusions.
It reminds me of our experience with lead exposure several decades ago. There was suspicion that lead was bad for the environment, owing to people with known exposure who had very severe neurologic outcomes. First it was adults in industry, and then we started noticing that children had the same problems. As we looked deeper and deeper into this, we started to see much more subtle effects from lead exposure. We are now starting to see the same type of story being explored and unfolding with the compounds that exist in our air and water.
The studies that we are talking about leave us with mixed impressions. On one hand, there was a suggestion that exposure to a large amount of certain environmental substances was associated with ADHD and related learning problems, as well as neuroimaging differences. On the other hand, another large Danish study found no association, leaving the connection between these exposures and ADHD uncertain. It is difficult at the present time to provide specific advice to families except to advocate for clean air and clean water, with the hope that these types of exposures are going to be minimized.
Medscape: In the 1980s, we saw children with astronomical lead levels requiring extensive chelation regimens. That was a wake-up call to the dangers of lead. Do you believe that it is going to take the same kind of extreme effects before we will address the downstream effects of PCB exposure?
Dr Lipkin: In contrast with lead, we are a little ahead of the game this time, which is good. Lead took everyone by surprise, and it sensitized us to be on the lookout for similar exposures that might be dangerous.
Now we have the Environmental Protection Agency. We have researchers who look at these exposures first in animal models, and then in humans. The public has been alerted as well. So hopefully, we will never get to the point at which these compounds will cause the serious problems that we recognized with lead. Instead, we will develop strategies to minimize maternal, fetal, and early childhood exposures to these compounds.
You never know what is lurking in the background. This is what we are paying attention to today, but what should we be paying attention to next is quite uncertain.
No Easy, Foolproof Diagnostic Test
Medscape: Should the diagnosis of ADHD still be primarily clinical, or are any promising biomarkers being used or investigated? For example, the US Food and Drug Administration (FDA) recently approved an EEG-based device to aid in the diagnosis of ADHD. Is there anything promising on the horizon that will make this diagnosis easier?
Dr Findling: ADHD is a difficult diagnosis to make accurately, not only because of the many comorbid conditions, but also because of the real lack of specificity of the symptoms. Many things can make a child appear restless or distractible. The list is almost endless.
The diagnosis is contingent on recognizing the expectations being placed on a child. What are the child's innate capabilities? What does the child look like over time? This is a highly heritable condition, and we would expect other members of the family to have similar challenges. Making a proper diagnosis requires an appreciation of development, educational demands, and what is expected of the child in a given circumstance at a given time.
The siren song of all of this is an easy test that is foolproof in making an accurate diagnosis. The more challenging the diagnosis, the more potentially alluring is that kind of solution. Sadly, there is no definitive yes or no, but one of the best ways to get the family's confidence is to provide a summation back to them to determine whether their information and concerns have been heard and integrated accurately from their perspective. That may be one of the best diagnostic tests I have. Before I even use the word "ADHD" or any psychiatric or behavioral diagnosis, if the parents are nodding their heads as if to say, "Yes, you understand our kid, thank you," then I can start putting names on what is going on.
I would suggest that to this day, the best diagnostic instrument is the ability to formulate thoughtfully what you have learned, which can't be done in a 5-minute visit; then provide feedback about your impressions; and finally, see whether there is accord between the informants and yourself. If there is, that is when you know you are barking up the right tree.
Dr Lipkin: We live in a very technological age, so it is always enticing to think that we can electronically make a diagnosis. However, when it comes to clinical medicine, we still have to listen to the patient, and they will tell you all that you need. An EEG is not going to tell you more than the family and patient.
Medscape: When you say "family input," I assume that also means information gleaned from teachers and daycare providers? How wide a net do you cast to obtain assessments of the child in various environments?
Dr Findling: Sometimes you have to give equal weight to those other settings. Let's say that you have a school setting where the demands on a given child are unrealistically high. A child who can't achieve what is being expected of him or her, for whatever reason, may look distractible, bored, and restless. That doesn't mean the child has ADHD. So you need to assess not only what the child is manifesting but also what is being expected of the child.
In that situation, you might have an overly demanding teacher. Conversely, if the family is very permissive, that sets different expectations from what would be considered reasonable in a typical school setting. If there is a discrepancy in impressions across informants, a clinician should understand why that discrepancy exists. When you have divergent information, it is important not to leap to a diagnosis, but to gain an understanding of the determinants of that disparity across impressions of a child's behavior. And the expectations matter.
Another example might be a child who is being victimized on the playground at school. That child might be disruptive in the classroom as a result of anxiety, or the hope of not being allowed out for recess to avoid being harmed. That is not ADHD. Many things can mimic ADHD, and it is the clinician's responsibility to understand those. No machine is going to do that.