Neuropsychological Assessment of Undergraduate Marihuana and LSD Users

College seniors who used LSD or mescaline performed within normal limits but significantly worse on the Trail Making Test compared to marijuana/hashish users and non-users, even after accounting for differences in alcohol consumption. The three groups were matched on pre-drug intellectual and personality traits. The study was replicated one year later with consistent results. The authors caution that these findings do not indicate organic brain dysfunction but suggest that prospective neuropsychological testing could be valuable.

Study at a glance

Abstract

An extended battery of neuropsychological tests was administered to three groups of college seniors (lysergic acid diethylamide [LSD]/mescaline users; marihuana/hashish users; and controls) who were matched on predrug usage intellectual and personality dimensions. The study was replicated one year later. In the combined-years' analyses, the three groups showed statistically significant differences only on the Trail Making Test: LSD/mescaline users performed within normal limits but significantly worse than either of the other two groups. Since the three groups also differed significantly in the extent of their alcohol usage, a covariance analysis was carried out that indicated that this variable did not account for the LSD/mescaline group's performance on the Trail Making Test. Inference about possible organic dysfunction cannot be drawn from these findings, but prospective neuropsychological testing might prove useful.