Are deficits in executive sub-processes simply reflecting more general cognitive decline in schizophrenia?

Background: Schizophrenia is associated with both global and specific cognitive deficits. We sought to investigate whether deficits in executive subcomponents differed in their relationship to global cognitive impairments.

Method: 95 patients were classified according to pre-morbid and current general cognitive ability as having either (a) intact pre-morbid and current general cognitive ability; (b) intact pre-morbid but deteriorated current ability, and (c) deteriorated both pre-morbid and current cognitive ability. All patients completed measures of verbal and spatial working memory, sustained selective attention, attentional set sifting, and inhibitory control.

Results: Deficits on both measures of working memory were associated with general cognitive ability. None of the attentional control deficits observed were associated with general ability. Further, spatial working memory deficits were also associated with more severe negative symptoms.

Conclusions: These results provide further evidence of the discreet nature of attentional deficits in schizophrenia. By contrast, this study suggests that working memory deficits may to some extent index more general cognitive decline. Awareness of such overlap is important for schizophrenia genetics studies where working memory measures has been used to index supposedly discreet aspects of cognitive dysfunction.