The relationships between schizophrenia symptom dimensions and executive functioning components

Research investigating the relationships between executive functioning impairments and the positive, negative, and cognitive schizophrenia symptoms has produced inconsistent results. This inconsistency may be due to the tendency to view executive functioning as a unified process as opposed to multiple fractionated processes. A fractionated model of executive functioning has been supported in several studies of various populations, but few schizophrenia studies have used the factor analytic methods of these studies to empirically determine separate executive functioning components, causing conclusions regarding the relationships between these components and schizophrenia symptoms to be unreliable. The purposes of the present study were to (1) identify separate components of executive functioning by conducting a factor analysis of the performance of individuals with schizophrenia on the Delis Kaplan Executive Function System (D-KEFS) and (2) investigate the relationships between executive functioning components and the three schizophrenia symptom dimensions by correlating the derived factor scores with the scale scores of the Positive and Negative Symptom Scale (PANSS). An exploratory factor analysis revealed two separate components: inhibition/set shifting and mental flexibility. The results showed that the symptom dimensions were differentially related to impairments in executive functioning, with both negative and cognitive symptoms associated with the inhibition/set shifting component, cognitive symptoms alone associated with the mental flexibility component, and positive symptoms unrelated to either component.