The relationship between delusions and depression in Alzheimer's disease

Objectives The aim of this investigation was to study the relationship between delusions and depression in Alzheimer's disease (AD). Design This was a cross-sectional, case control study. Setting Neuropsychiatry Service, the Johns Hopkins School of Medicine, USA. Participants 303 community-residing patients with probable AD according to NINCDS/ADRDA criteria were included in the study. Seventy-five patients with delusions only were compared to a control group of 228 patients who had neither delusions nor hallucinations. Patients with only hallucinations or both delusions and hallucinations were excluded. Measures Patients were assessed clinically for the presence of delusions using the DSM-IV glossary definitions. They were also rated on standardized measures of depression, cognitive impairment, staging of dementia, general medical health, and functional impairment. Results There was an association between delusions and depression among patients with AD. Before adjustment for other variables, the presence of depression conferred a 1.8-fold (95\% confidence intervals (CI) = 1.0-3.1; p = 0.04) higher risk of delusions. After adjustment for multiple other variables, this risk increased further to 6.8-fold (95\% CI = 2.1-21.6; p = 0.001). Conclusions Delusions in AD are strongly associated with depression after statistical adjustment for all confounding variables, which might distort this association. This finding has implications for our understanding of the etio-pathogenesis and management of delusions and depression in AD. Copyright (C) 2002 John Wiley Sons, Ltd.