Negligible effects of depression on verbal and spatial performance in Alzheimer's disease.

We examined whether a diagnosis of depression affects verbal and visuospatial performance in Alzheimer's disease (AD). Using data from a population-based study, persons with AD and depression (AD/D), AD alone and a control group of normal older adults were compared in two tests of verbal ability (category and letter fluency) and two tests of visuospatial skill (block design and clock drawing). As expected, there were clear AD-related deficits across all cognitive tasks. More importantly, the AD and AD/D groups were indistinguishable on all task variables. The lack of effects of depression was discussed relative to the view that those symptoms of this disease which are especially detrimental to cognitive functioning (e.g. concentration difficulties, lack of interest, loss of energy) may already be present in AD as a result of the neurodegenerative process.