Epidemiology of mental disorders in middle age and late life: conceptual issues.

One of the "uses of epidemiology" described by Morris (1) is to complete the clinical picture in describing the natural history of disease. This arena for epidemiologic inquiry is especially important in relation to psychiatric disturbances. Most adults with psychiatric complaints and symptoms, especially older adults, do not receive care in the mental health sector (2-4). Distorted views of the nature of these disturbances can result when studies sample only from those individuals who are treated by psychiatrists or other specialists (5, 6). This has led to greater interest in previously neglected venues such as nursing homes, home care, and the primary health care services (7-12). Improved detection and treatment of mental disturbances in primary health care may be an essential key to enhance the effectiveness of community treatment (13). Completing the clinical picture is a critical task indeed. The purpose of this review is to introduce several conceptual issues important to completion of the clinical picture in epidemiologic research on risk and protective factors for mental disorders across the life course, with a focus on adulthood and late life. These issues are 1) the measurement of psychiatric disturbances in populations, 2) methodological considerations in surveys of older adults, and 3) the life course perspective on risk factors for psychiatric disturbances.