To the Editor.
—In the article by Phibbs et al,1 "The Neonatal Costs of Maternal Cocaine Use," the abstract did not adequately reflect the results presented in the article. In the results section of the abstract, the authors state that the cost of neonatal care until medically cleared for discharge was significantly higher for cocaine-exposed than for non-cocaine-exposed infants. This leaves the reader to assume that cocaine exposure is the factor that explains the impressive difference.However, the two populations compared in the study (cocaine-exposed and non-cocaine-exposed) differed in several important ways. These included use of other substances, adequacy of prenatal care, smoking, racial composition, age, and gravidity of mothers. Each of these variables could be important confounders and (as the authors rightly demonstrated) should be controlled in drawing conclusions as to the effect of the cocaine exposure itself.In the body of the text the authors are