Patterns and clinical correlates of neuropsychologic deficits in patients with schizophrenia

Neuropsychologic deficits are prevalent among schizophrenic patients and are closely associated with pathogenesis and outcome. The pattern, extent, severity and contributing factors to such deficits remain to be examined in Taiwanese schizophrenic patients.

A total of 122 schizophrenic patients and 94 healthy subjects for comparison were assessed by a comprehensive neuropsychologic test battery covering the eight cognitive domains of verbal ability, visual spatial ability, abstraction/execution, verbal memory, visual memory, perceptual/motor ability, mental control and attention. The relationships among cognitive deficits, demographic characteristics, clinical historical variables and clinical symptoms were further explored by multivariate regression analysis.

A pattern of selective deficits superimposed on a generalized deficit was found for schizophrenic patients as a group. The mean overall deficit was 1.93 standard deviations below the control mean, and abstraction/execution, verbal memory, visual memory and attention were relatively impaired among the eight cognitive domains. However, there was also marked heterogeneity in individual performances in that 24.2%, 46.2% and 29.5% of patients performed at within normal range, moderately impaired and severely impaired levels, respectively. Duration of illness substantially affected the profile and severity of the deficits, suggesting a progressive deteriorating course in neuropsychological performance. The major predictors of cognitive deficits were number of formal years of education achieved and concurrent severity of disorganization symptoms.

In a large sample of schizophrenic patients who underwent comprehensive neuropsychologic evaluation, the current results confirmed that cognitive deficits were prevalent but not a universal feature within schizophrenia. The selective impairment pattern also confirmed that such deficits were mainly in frontal and frontotemporal related functions. Despite evidence suggesting that disease chronicity entailed a decline in selective cognitive domains, the trajectory of the neuropsychologic deficits remains to be examined by further longitudinal studies.