A risk factor strategy for investigating affective illness.

A "risk factor" approach to affective illness is outlined. Characteristics which are correlated with vulnerability to depression (or mania) should be sought and attempts made to either modify them or elucidate a pathophysiologic link between the characteristic and the illness. Genetic factors, biochemical factors, life events, demographic variables, and behavioral factors may be examined under the assumption that affective illness is multifactorially determined. Identification of these risk factors by a prospective epidemiologic study in a geographically delimited area is discussed; the risk factor model is compared with the high-risk model.