Criterion-related validity of the Geriatric Depression Scale in Alzheimer's disease.

The effect of cognitive impairment on the criterion-related validity of the self-report Geriatric Depression Scale (GDS) was investigated in community-dwelling older adults. The GDS was administered to subjects with Alzheimer's disease (AD; n = 715) and normal cognitive function (NC; n = 93). The criteria consisted of the diagnosis of major depressive disorder and the total score on Hamilton Rating Scale for Depression, each derived from structured interview with a collateral informant to circumvent the effect of cognitive impairment on criterion measurement. Agreement between the GDS and both criteria was substantially attenuated in AD relative to NC subjects, differences primarily reflecting a lower than expected rate of item endorsement on the GDS in AD. A decrement in GDS validity coefficients was measurable across a broad range of cognitive impairment, suggesting limited utility of the scale in AD.