Genetic epidemiology of psychiatric disorders

Advances in standardized definitions of major psychiatric disorders has dramatically enhanced our ability to reliably characterize behavioral phenotypes for genetic studies. The application of family, twin, adoption, and genetic marker paradigms to this domain has offered new opportunities for understanding the respective roles of genetic and environmental factors for classes of disorders that affect large percentages of the general population. However, previous research has been impeded by several factors, notably a lack of biologic validity of diagnostic categories as well as the genetic complexity of psychiatric disorders. In fact, the discovery of the breast and the ovarian cancer susceptibility gene (BRCA1) witnesses the importance of maximizing disease homogeneity among study subjects. The application of genetic study paradigms to guide definitions of the thresholds and boundaries of psychiatric syndromes (and to refine the precisions of phenotypic definitions) will hopefully enhance the identification of homogeneous subtypes, and thereby increase the power of linkage studies in elucidating their genetic basis.