Executive function in first-episode schizophrenia: a three-year prospective study of the Hayling Sentence Completion Test.

In recent decade, deficits in the mechanism of Supervisory Attentional System (SAS) have become increasingly influential in explaining the nature of dysexecutive syndrome experienced by schizophrenic patients. The SAS model is characterized by having a detailed sub-classification of specific executive function components, among which semantic inhibition has been investigated using the Hayling Sentence Completion Test (HSCT). Several studies thus far have indicated that schizophrenic patients show impairment in HSCT performance. However, HSCT data concerning first-episode patients is still scarce. Besides, as previous HSCT studies were all cross-sectional in nature, they were not able to assess changes in HSCT performance over time. In order to address the paucity of knowledge about the longitudinal trajectories and correlates of semantic inhibition deficits in early schizophrenia, this paper reports a three-year prospective study of HSCT performance in medication-naïve, first-episode patients with schizophrenia-spectrum disorders. HSCT performance was assessed in 34 patients at four times over a period of three years, while the 34 healthy controls were assessed once. We found that medication-naïve patients demonstrated impairment in the inhibition condition in HSCT as compared to controls, but not in the initiation condition. Such HSCT impairment gradually improved in the three years following the first psychotic episode; however, HSCT performance did not predict improvement in negative or positive symptoms over the three-year period. The present findings suggest that semantic inhibition impairment is a specific deficit in schizophrenia that may require early intervention efforts, with the goal of facilitating more successful verbal communication and thereby better interpersonal functioning.

Executive function in first-episode schizophrenia: a three-year longitudinal study of an ecologically valid test.

Executive function impairment is a key cognitive deficit in schizophrenia. However, traditional neuropsychological tests of executive function may not be sensitive enough to capture the everyday dysexecutive problems experienced by patients. Additionally, existing literature has been inconsistent about longitudinal changes of executive functions in schizophrenia. The present study focuses on examining the longitudinal change of executive functions in schizophrenia using the Modified Six Elements Test (MSET) that was developed based on the Supervisory Attentional System model and shown to be sensitive to everyday dysexecutive problems. In the present study, MSET performance was assessed in 31 medication-naïve first-episode schizophrenic patients at four times over a period of three years, while the 31 normal controls were assessed once. Patients demonstrated impairment in MSET as compared to controls. Importantly, the MSET impairment persisted from the medication-naïve state to clinical stabilization and the three years following the first psychotic episode though patients improved in a conventional executive test (Modified Wisconsin Card Sorting Test). Performance was not related to intelligence, educational level, symptom changes, age-of-onset, or duration of untreated psychosis. Better MSET performance at medication-naïve state predicted improvement in negative and positive symptoms over the three-year period. These findings may suggest that MSET impairment is a primary deficit in schizophrenia that occurs early in the course of the illness and remains stable irrespective of clinical state for at least three years following the first episode of schizophrenia.