The distinction between the natural changes of aging and the clinical symptoms of disease is particularly relevant when considering mental changes in late life. Clinical and research advances in geriatric psychiatry document that cognitive impairment and depressed mood, for example, are not intrinsic characteristics of growing old but that they can be indicative of mental illness. Epidemiological investigations applied to psychiatric problems have shown that mood disorders, dementia, schizophrenia, and alcohol-related disorders account for why the aged use psychiatric services so much (Blazer, 1995). The prevalence of depression has been estimated at between 2% and 4% in representative samples of noninstitutionalized individuals older than 65. The rates reach 15% and even higher when subclinical depressions are included in the sampling of older age groups (Gatz, Kasl-Godley and Karel, 1996). Depression and dementia are very prevalent among elderly patients in psychiatric units and nursing homes (Anthony and Aboraya, 1992; Gurland, 1996). Depression, as a nosological entity or as a psychiatric symptom, commonly occurs during primary medical care and ambulatory medical settings. The association between affective disorders and physical illness is manifested in a wide range of medical problems including stroke, Parkinson's disease, arthritis, endocrine disorders and renal and hepatic failure, as noted in Chapter 9. Among US community residents 65 years and older, the rate of dementia is estimated as 4.5%, with Alzheimer's disease and multi-infarct disorders accounting for the majority of cases of dementia. The prevalence of dementia rises rapidly with age, reaching 20% in patients older than 80. Alcohol abuse and dependency are also frequently detected among older men in psychiatric services and hospital and outpatient medical clinics.