Patterns of cognitive impairment among alcoholics: are there subtypes?

The mild generalized dysfunction hypothesis of alcohol abuse's deleterious effects on cognitive processes has gained support from a number of studies in which detoxified alcoholics have a lower mean performance level than peer controls on a variety of neuropsychological tests. This approach might obscure consistent but different patterns of preserved and impaired cognitive performance among subgroups of alcoholics, suggestive of alternative hypotheses. To test this possibility, neuropsychological test data from two large, independent samples of alcoholics (sample 1, n = 143; sample 2, n = 130) and controls (sample 1, n = 97; sample 2, n = 83) were subjected to separate centroid hierarchical cluster analyses. For both samples, the majority of alcoholics (94% and 94%) exhibited a pattern of impaired verbal and nonverbal performance and deficits in memory and perceptual motor skill, with normal motor skill. The alcoholics who did not fit this pattern showed more severe or wide-ranging impairments. These findings indicate that empirical support for the mild generalized dysfunction hypothesis of alcoholics' cognitive deficits is not an artifact of averaging.