Major depression in Down's syndrome

Five patients with trisomy 21 (Down's syndrome (DS)), referred to us for evaluation of dementia, were instead found to have major depression. All had shown cognitive and behavioural deterioration and this had led to a mistaken diagnosis of Alzheimer's disease in two. We outline and contrast the features of major depression and Alzheimer's disease in DS, and suggest that electroconvulsive therapy is an effective treatment for major depression in DS.