Is there a cognitive phenotype for schizophrenia: the nature and course of the disturbance in cognition?

Cognitive deficits in schizophrenia have been a recent focus of researchers. Although long thought to be the secondary effect of medication, institutionalization, or symptoms, cognitive dysfunction is now thought to be an independent core deficit. This review covers evidence for the cognitive domains that appear to be most impaired from studies of: (i) first episode patients; (ii) cognitive stability; (iii) the universality of deficits; and (iv) deficits in non-psychotic relatives. All of these serve to strengthen the notion that schizophrenia patients and their relatives are most impaired in attentional, executive, verbal declarative memory, and verbal fluency functions. These cognitive domains are subserved by neural networks linking frontal, anterior cingulate, and temporal-limbic regions, and may represent cognitive endophenotypes in the search for genetic markers. The search for causes of schizophrenia might be enhanced by the further elucidation of neuropsychological deficits in patients and relatives.