The relationship between depression and cognition in older adults: a cross-validation study

The relationship between depression and cognition in older adults has become a topic of extensive research and clinical interest. Results of previous research are limited, however, by sampling and methodological problems. Small sample sizes and the treatment of depression as a dichotomous variable may be major factors that limit data interpretation in previous studies. The present sample of 220 geriatric medical patients was split into a validation and a cross-validation sample specifically to test the hypothesis that depression is an independent predictor of cognition. Multiple regression analyses, controlling for the direct effects of demographic factors, found that Geriatric Depression Scale scores were consistently a significant predictor of Dementia Rating Scale and Logical Memory scores. Overall, GDS scores accounted for approximately 8% of unique variance for both measures of cognition. Demographic factors, particularly age and race, were also significant predictors of cognitive test scores. These data were interpreted as providing support for the hypothesis that level of depression predicts level of cognitive functioning.