A retrospective study of premorbid ability and aging differences in cognitive clusters of schizophrenia.

This retrospective, cross-sectional study evaluated whether age-related differences in patterns of cognitive deficit exist among four cognitively based schizophrenia subgroups. These subgroups had previously been identified through cluster analyses of a battery of abstraction and problem-solving tests in large samples. Evaluation of estimated premorbid intellectual ability and postmorbid cognitive functioning stratified by decade from the twenties through the fifties revealed different patterns across the schizophrenia subgroups and a clinical comparison sample. A near normal cognitive subgroup demonstrated relatively high premorbid intellectual ability and a pattern of age differences similar to the comparison sample, with the exception of deficits on the Wisconsin Card Sorting Test that were detectable in the twenties and remained stable thereafter. In contrast, a subgroup characterized by severe, pervasive cognitive deficit demonstrated low premorbid intellectual ability and extremely low test scores across the four decades studied. The remaining clusters were characterized by moderate cognitive impairment and showed age differences suggestive of a decline in cognitive function around the time of illness onset that remained stable. Results provide further support for the validity of these subgroups and encourage continued efforts to identify cognitively based candidate schizophrenia subtypes.