Measuring Changes in Functional Status Among Patients With Schizophrenia: The Link With Cognitive Impairment

Abstract

Cognitive impairment associated with schizophrenia (CIAS) includes neuropsychological deficits in attention, working memory, verbal learning, and problem solving. These deficits have been shown to be linked to impairment in functional status (eg, social behavior, work performance, and activities of daily living) among patients with schizophre- nia in cross-sectional studies. Less is known about the rela- tionship between cognitive and functional change over time, such as potential functional implications of treatment- related improvement in CIAS. The purpose of this review is to summarize research on the association between change in CIAS and change in functional status, to discuss respon- siveness of functional outcomes measures, and to provide recommendations for future research and measure develop- ment. Nine longitudinal studies were located on the link between CIAS and functional status, and 8 functional outcomes measures were used across these studies. The 9 studies offer initial support for a link between change in cognitive function and change in functional status. How- ever, inconsistentfindings across studies indicate that avail- able research is preliminary, and substantial questions remain unanswered. Shortcomings of functional status measures are noted: most instruments were not developed for the target population, and none have demonstrated re- sponsiveness to cognitive change among schizophrenic patients. It is recommended that new functional outcome measures be developed that are specifically designed to be responsive to change in cognition, with domains previ- ously shown to be related to cognitive ability. When creat- ing new functional outcomes measures for assessment of patients with schizophrenia, responsiveness to change in CIAS should be evaluated as part of the development and validation process.