A review of longitudinal studies of cognitive functions in schizophrenia patients.

Even though the idea that schizophrenia is a neurobehavioral syndrome has become a mainstream position, there is no consensus on the precise nature of the cognitive and neuropsychological impairment. Research on cognitive dysfunctions in schizophrenia has been directed toward discriminating stable dysfunctions (traits) from symptom-linked (state) deficits. A longitudinal study design is the only one that can provide answers to the question of the stability of psychological functions. This article reviews 15 studies with a followup of at least a year. The main conclusion drawn from these studies is that after the onset of schizophrenia, cognitive deficits are relatively stable over long periods. No support for a decline in cognitive functions is found. Thus, schizophrenia does not appear to be a degenerative process, but rather a static encephalopathy. Whether or not the cognitive deficits found in schizophrenia can be remediated is still an open question that needs to be examined.