Importance of subtyping in psychopharmacogenetic studies.

Research on the importance of genetic and environmental risk factors (multifactorial) in the etiology of mental disorders and substance use disorders (alcoholism) is now growing rapidly. Biological and psychological studies in this field should include basic concepts of medical genetics and take heterogeneity (multidimensionality) of mental disorders into account. One of the best means to cope with heterogeneity is to redefine the diagnostic phenotype at different levels: biochemical, behavioral, familial. Data are presented where the introduction of different quantitative definitions of the phenotype and their analysis by multivariate technics are used for better understanding of alcoholic disorders.