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May 22, 1996

Cognitive Effects of Marijuana-Reply

Author Affiliations

McLean Hospital Belmont, Mass

JAMA. 1996;275(20):1547. doi:10.1001/jama.1996.03530440025030

In Reply.  —We certainly agree with Drs Scheier and Botvin that heavy marijuana users might have antecedent neuropsychological and behavioral deficits to a greater degree than occasional marijuana users and that this phenomenon could account for the differences observed in our study. In fact, we address this question in detail in our article. However, our analyses controlling for verbal IQ and reported Scholastic Aptitude Test scores both suggested that premorbid deficits were unlikely to account for the differences in cognitive functioning observed. Further, we were unable to detect clear differences between even the heaviest and the lightest marijuana users on a number of psychological and behavioral measures.1 Similarly, in the other large recent study of the residual cognitive effect of marijuana,2 an analysis using test scores obtained years earlier, prior to marijuana use, also suggested that premorbid deficits could not account for the findings. Thus, the burden of