Risk research in affective disorders and alcoholism: epidemiological surveys and trait markers

Traditional designs in risk research have been in the form of epidemiologic surveys aimed at assessing a genetic contribution or search for broader indicators of vulnerability, resulting from the interaction of both nature and nurture. Recently, an interest in biological markers has resulted in the search for possible trait markers identifying more specifically, individuals with a life-long risk for an illness that may be expressed or not. The contributions, limitations and evolution of these strategies are reviewed in the syndromes of affective disorders and alcoholism. Recommendations include the use of biotypes rather than phenomenotypes for the diagnosis of the index case. Current promising approaches include the study of pedigrees biased towards a particular variable, a discriminant analysis of the variation in expressivity of the syndrome and the genetic linkage studies. While there is so far no established trait marker, research strategies are emerging and withstanding the test of time. The present technological explosion will undoubtedly further our understanding of risk factors.