Cognition in schizophrenia: Natural history, assessment, and clinical importance

Retrospective studies have demonstrated that Schizophrenie patients often have poor premorbid cognitive function and social adjustment. Cross-sectional studies of the cognitive performance of schizophrenic patients aged 20 to 90 years indicate that there is a gradual decline in cognitive function throughout the adult life span. Comparison studies of Alzheimer’s disease patients, geriatric schizophrenic patients, and normal subjects indicate that Alzheimer’s disease patients have marked impairments in memory and executive function, with impairments in language and constructional ability developing later in the disease. In contrast, schizophrenic patients manifest more general cognitive impairment with less impairment in memory andmore impairment in visuospatial and language ability early in the course of dementia. Neuropathological findings indicate that the dementia associated with schizophrenia is pathophysiologically distinct from that of Alzheimer’s disease. Functional impairment in patients with schizophrenia is closely related to cognitive deficit but not to positive and negative psychotic symptoms. Based on these findings, assessment strategies for evaluation of antipsychotic drug therapies are proposed to incorporate measures of psychosis, cognition, and function.