Disorganization and cognitive impairment in schizophrenia: independent symptom dimensions?
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Cognitive deficits are increasingly considered as essential in schizophrenic disorders. Positive symptoms and cognitive deficits have been found to be independent, whereas negative symptoms show only weak correlations to cognitive impairment. However, the relationship to a third symptom dimension, disorganization, is yet unclear. In a sample of n = 151 schizophrenia inpatients (DSM-IV/SCID) we assessed cognitive impairment using a comprehensive neuropsychological test battery and symptoms of schizophrenia applying the Positive and Negative Syndrome Scale (PANSS). Factor analyses resulted in three neuropsychological (attention, memory, abstraction) and five symptom factor scores (negative, impulsiveness, positive, disorganization, depression). The disorganization factor did not correlate significantly with any of the neuropsychological factor scores. Even after controlling for different demographic and clinical variables partial correlation coefficients did not reach a significant level. Thus, we could not confirm the previously reported associations between disorganization and measures of cognitive impairment. Despite a considerable conceptual overlap between interview based symptom ratings and classic neuropsychological tests the empirical association is limited. Our results suggest that disorganization and cognitive impairment represent different symptom dimensions.