Heterogeneity of schizophrenia: a study of individual neuropsychological profiles

Based on a strategy developed by Seidman et al. (Seidman, L.J., Faraone, S.V., Kremen, W.S., Pepple, J.R., Lyons, M.J., Tsuang, M.T., 1993. Neuropsychological dysfunctions in the non-psychotic first-degree relatives of schizophrenic patients, Poster presented at the annual meeting of the Society for Research and Psychopathology. Chicago, IL) we examined neuropsychological heterogeneity in schizophrenia using clinical neuropsychological descriptions of individual cases as the starting point. We blindly rated neuropsychological profiles of 74 schizophrenia patients and 91 normal controls based primarily on prototypes from the clinical literature in neuropsychology. Patients were classified as having the following profile types: within normal limits (WNL) (23%, n=17), frontal/abstraction (46%, n=34), widespread/diffuse (14%, n=10), left temporal/verbal memory (8%, n=6) and other (9%, n=7). As expected based on our classification scheme, the groups had different profile shapes (group x function interactions). They were also significantly different from one another in terms of overall severity (main effects); however, severity differences were not inherent in the definition of all groups. Longer duration of illness and greater overall cognitive impairment were observed as one went from the left temporal to the frontal to the widespread groups. Longitudinal studies are needed to determine whether the different neuropsychological profiles reflect true subgroup differences or within-person change over time. Further research-probably including neuroimaging and genetic studies-will also be needed to determine the validity and the utility of this strategy for identifying neuropsychological profile types.