Attention-Deficit/Hyperactivity Disorder Treatment and Later Drug Use

To the Editor.—

I was fascinated with the article by Barkley et al¹ on stimulant treatment for attention-deficit/hyperactivity disorder and risk of later drug abuse. The authors have tried to answer a question that worries many.

I am quite confused by their conclusion, which seems at clear odds with their data. They found, unfortunately, that treatment with stimulant medication in high school is significantly associated with the risk of ever trying cocaine. That this is a valid conclusion is supported by their finding that treatment with stimulant medication in childhood is associated with cocaine use in adulthood, although after adjusting for “disease severity” and the presence of conduct disorder, the association was no longer significant.

The authors work extraordinarily hard to explain to the reader why the first finding, which is statistically significant, is actually not real. The naïve reader may wonder why the authors are so invested in undermining their own carefully performed results.

It would make more sense to say that patients with conduct- disorder symptoms, or very severe attention-deficit symptoms, should not be treated with stimulant drugs because it appears that, in this subgroup, such treatment may be associated with an increased risk of cocaine use in adulthood. Or the authors could conclude that their population cannot answer the question that is being asked, because they did not compare a “treated with behavioral/psychotherapy plus stimulants” group versus a “treated with behavioral/psychotherapy without stimulants” group. In support of this conclusion, the authors do note …