Neuropsychological differences between alcohol-dependent and cocaine-dependent patients with or without problematic drinking

The present study evaluated differences among three groups of substance abusers, abstinent for 1-5 months. One group was composed of 17 alcohol-dependent patients. The other two groups were composed of cocaine-dependent patients who scored below (n = 29) or above (n = 18) the median Michigan Alcoholism Screening Test (MAST) score for the cocaine-dependent group in total. The Shipley Institute of Living Scale was administered to all subjects. An ANOVA, with age as a covariate, revealed that the cocaine-dependent group with lower MAST scores exhibited statistically significant impairments on the Shipley abstraction subtest and on total IQ relative to the two other groups. There were no group differences on the verbal subtest. The abstraction and IQ deficits in the lower MAST score cocaine-dependent group could not be explained by decreased verbal abilities, a greater duration or frequency of cocaine use, or by a higher prevalence of Antisocial Personality Disorder. However, a chi 2 analysis revealed that this group contained more individuals who used cocaine in its 'freebase' or smoked form. Since the two cocaine-dependent groups were comparable in demographic and psychological characteristics, but had different levels of cocaine exposure, the results suggest that the decrements in abstraction scores reflect a cocaine-related effect.