The components of executive functioning in a cohort of patients with chronic schizophrenia: A multiple single-case study design☆

We examined the fractionation of executive functioning performance in ninety patients with schizophrenia, who were tested for initiation, sustained attention, switching/flexibility, attention allocation and impulsivity/disinhibition. The participants were also given tests of general intelligence and memory. We analysed the executive functioning performance of individual patients against normative data from our laboratory, and summary scores for all of the executive functioning components were computed. For each component, participants were classified as having impairment with a test performance of 1.5 standard deviations or more from the norm of the corresponding test. Of all of the participants, 27.8% (n=25) demonstrated poor performance in all of the components, and 5.6 % (n=5) exhibited intact or fair performance in all of the components. Furthermore, 18.9% (n=17) showed intact or fair performance in one component, 16.7% (n=15) in two components, 21.1% (n=19) in three components and 10% (n=9) in four components. The groups did not differ in education, gender or duration of illness, but the group that showed impaired performance in all of the components demonstrated the most severe psychotic symptoms after controlling for background intelligence, age and medication. The differential breakdown for the executive functioning performance across the participants suggests that the fractionation of central executive functioning occurs in schizophrenia.