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

Cognitive Subtypes of Schizophrenia Characterized by Differential Brain Volumetric Reductions and Cognitive Decline

“…In the clinical grouping method (eMaterial in the Supplement), the compromised group was also underrepresented compared with the previous studies of these patients 3,4 and other studies. 6,18,19 Despite having apparently stable IQ levels, the putatively preserved subgroup had deficits on attention/processing speed, a finding consistent with the previous studies of these patients. 3,5,20,21 In the present study, the 2 deteriorated groups were distinguished by a larger mean decline in IQ (11 vs 7 points), and the severely deteriorated group had additional deficits in verbal fluency, negative symptom severity, and cortical and subcortical brain volumes beyond that found in the moderately deteriorated group.…”

Mood congruent psychotic symptoms and specific cognitive deficits in carriers of the novel schizophrenia risk variant at MIR-137

“…In both cases, the deficits were more prominent in a 2-groups comparison of homozygous risk carriers versus the other genotype groups combined. Previous work by our group suggested that deficits in attentional control disassociate from more general cognitive deficits within the schizophrenia population [ 7 ]. Whether the subtlety of these effects reflects this risk variant's particular association with an affective form of psychosis in which cognitive deficits are less pronounced, or simply reflect M a n u s c r i p t 11 the modest cognitive effects of this variant remains to be elucidated.…”

Specific cognitive deficits in a group at genetic high risk of schizophrenia

“…A further difficulty lies in identifying specific deficits amongst a more general decline in cognitive ability present in schizophrenia (Donohoe et al 2006). Deficits in general cognitive function, usually measured in terms of deficits on IQ measurements, often yield larger effect sizes than obtained for more specific cognitive impairments (Heinrichs & Zakzanis, 1998), and show evidence of heritability (Goldberg et al 1990).…”