'Don't know' responses in elderly demented and depressed patients

The suggestion that patients having depression with reversible dementia make more "don't know" responses to cognitive questions than do demented patients was tested. Inpatients were administered the Mini-Mental Status Examination (MMSE) on admission and shortly before discharge. Errors and "don't know" responses were recorded. Groups were defined as (1) demented (n = 20; diagnosis of dementia, entrance and exit MMSE less than 24) and (2) depressed with reversible dementia (DRD, n = 11; diagnosis of major depression, entrance MMSE less than 24, exit MMSE greater than 24, delta MMSE greater than 3). Groups differed significantly on MMSE scores and errors, with demented patients scoring lower and making more errors than the DRD group. Groups did not differ significantly in "don't know" responses. Comparisons between groups on sections of the MMSE showed that demented patients scored significantly lower and made more errors than DRD patients only on the orientation section of the MMSE. The results suggest that DRD patients do not make more "don't know" responses than demented patients; however, demented patients make more errors on orientation questions.