UC San Diego

Executive functions are among the strongest neurocognitive predictors of functional disability among people with schizophrenia. However, there remains considerable debate about what constitutes executive functions, the extent to which they are uniquely impaired above and beyond other cognitive abilities, and their relationship with clinical and everyday functioning correlates of schizophrenia. The aim of the current study was to simultaneously assess multiple executive functioning abilities, as measured by the Delis-Kaplan Executive Function System (D-KEFS) among people with schizophrenia (SCs) compared to demographically-matched healthy comparison subjects (HCs), to assess for differential impairment among specific multi -level abilities and basic cognitive skills, to clarify the construct of "executive functions" in schizophrenia, and to examine the relationship of specific executive functions to psychopathology and everyday functioning. In this study, SCs, on average, had consistently worse multi- level executive functions in comparison to HCs. The differences between ipsative performances on multi-level tasks (e.g., switching) and basic cognitive tasks (e.g., motor speed) were greater among SCs than among HCs on some, but not all executive functioning tasks. Although the specific member components varied among SCs and HCs, exploratory factor analyses with the two groups examined separately, both revealed two factor solutions (cognitive flexibility/switching and abstraction/conceptualization). Latent profile analysis of the D-KEFS scores in the SCs indicated three distinct profiles, i.e., mildly impaired, average, and high average-to-superior. The high functioning group was characterized by higher levels of premorbid functioning (as estimated with education and word reading performance). Within-group, ipsative comparisons indicated that those in the mildly impaired group did worse on abstraction tasks and better on switching tasks compared with each subject's own respective mean performance, while those in the high average group had the opposite pattern. Path models indicated intact working memory as necessary for intact cognitive flexibility, and intact abstraction as necessary for intact logical reasoning and sorting abilities. Severity of thought disorder was associated with worse performance in terms of cognitive flexibility/switching and abstraction/conceptualization; there were no other significant relationships found between severity of psychopathology and executive functioning. Both D-KEFS factors were also significantly correlated with functional capacity, but not level of independence in current living situation, or quality of life.