Neurocognitive Impairments in Deficit and Non-Deficit Schizophrenia and Their Relationships with Symptom Dimensions and Other Clinical Variables

Abstract

Background: Deficit schizophrenia (DS) has been proposed as a pathophysiologically distinct subgroup within schizophrenia. Earlier studies focusing on neurocognitive function of DS patients have yielded inconsistent findings ranging from substantial deficits to no significant difference relative to non-deficit schizophrenia patients (NDS). The present study investigated the severity and characteristic patterns of neurocognitive impairments in DS and NDS patients and their relationships with clinical variables.

Methods: Attention, ideation fluency, cognitive flexibility and visuospatial memory function were assessed in 40 DS patients, 57 NDS patients, and 52 healthy controls by a comprehensive neuropsychological battery.

Results: Both schizophrenia subgroups had overall more severe cognitive impairments than controls while DS performed worse on every neuropsychological measure except the Stroop interference than the NDS patients with age and education as the covariates. Profile analysis found significantly different patterns of cognitive profiles between two patients group mainly due to their differences in attention and cognitive flexibility functions. Age, education, illness duration and negative symptoms were found to have the correlations with cognitive impairments in the NDS group, while only age and the negative symptoms were correlated with the cognitive impairments in the DS group. Multiple regression analyses revealed that sustained attention and cognitive flexibility were the core impaired cognitive domains mediating other cognitive functions in DS and NDS patients respectively.

Conclusions: DS patients exemplified worse in almost all cognitive domains than NDS patients. Sustained attention and cognitive flexibility might be the key impaired cognitive domains for DS and NDS patients respectively. The present study suggested the DS as a specific subgroup of schizophrenia.

Fig 1. Profile analysis for neuropsychological tests and cognitive domains of DS and NDS groups.

Note: Profile analysis for (a) neuropsychological tests and (b) cognitive domains of DS and NDS groups. ST word: Stroop word only; ST col: Stroop color only; TMTA&B: Trail Making Tests A&B; DVT: Digit vigilance test; ANT: Animal Naming test; COWAT: Controlled Oral Word Association test; ST int: Stroop interference test; SP: Spatial processing (Block Design); WAIS-RC: Wechsler adult intelligence scale (Block Design, Chinese version); SV: Sustained vigilance/attention; IF: Ideation fluency; CF: Cognitive flexibility; VM: Visuospatial memory. The error bars on Fig 1 was standard errors.

Fig 2. The multiple regression analyses for relationships between clinical features and cognitive domains in DS and NDS group, respectively.

Note: The relationships between clinical variables and cognitive domains impairments in (a) DS group and (b) NDS group were carried out with the hierarchical regression analyses. The numerical values represent standardized beta weights.