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Scientific American has a good story by Edmund S. Higgins suggesting that might be the case. As the story notes, the evidence for such a toll is still preliminary. But the story's opening, which tells of a parent seemingly overeager to medicate a child who didn't need it, gives an idea of why the question is more important than we might like.:
At the time of this visit, the boy was off the medication, and I conducted a series of cognitive and behavioral tests on him. He performed wonderfully. I also noticed that off the medication he was friendly and playful. On a previous casual encounter, when the boy had been on Adderall, he had seemed reserved and quiet. His mother acknowledged this was a side effect of the Adderall. I told her that I did not think her son had attention-deficit hyperactivity disorder (ADHD) and that he did not need medication. That was the last time I saw her.
