Impairments in executive functioning in patients with remitted and non-remitted schizophrenia

Objective: Although deficits in executive functioning are prominent in schizophrenia, some patients in remission have shown significantly higher levels of neurocognitive functioning than patients not in remission. However, no consensus on the relationship between neurocognitive functioning and the severity of symptoms has been reached. Additionally, previous studies have mainly examined the primary symptom domains of schizophrenia without considering the influence of anxiety symptoms, which are likely to influence neuropsychological performance. The aim of the present study was to compare the executive functioning of normal controls and with that of patients with schizophrenia in acute and remitted states. We further examined associations between impaired executive functioning in patients and anxiety levels.

Methods: Using a battery of tests assessing executive functioning including subtests of the Cambridge Neuropsychological Automated Test Battery (CANTAB) and the short form of the Korean Wechsler Adult Intelligence Scale (K-WAIS), we assessed 54 patients with schizophrenia and 33 normal controls.

Results: Our results showed that patients with non-remitted schizophrenia obtained significantly lower estimated IQ scores than did normal controls. They also exhibited longer reaction times on the Choice Reaction Time (CRT) test and the Stop Signal Test (SST) subtests of CANTAB and a greater number of total errors and errors that occurred before the extradimensional stage (i.e., pre-ED errors) on the Intradimensional/Extradimensional Shift (IED) subtest of CANTAB. Furthermore, those with schizophrenia in acute states showed significantly slower stop signal reaction times (SSRT) on the SST than did those with remitted schizophrenia and healthy controls. Finally, differences in the pre-ED errors and total adjusted errors on the IED became insignificant when scores on the Beck Anxiety Inventory (BAI) were entered as the covariate, whereas other significant differences remained when these scores were entered.

Conclusion: Differences in executive functioning exist between patients with schizophrenia and healthy controls; these differences can be largely attributed to the relatively poor performance of patients in an active state.