Introduction to psychiatric genetics: Progress in the search for psychiatric disorder susceptibility genes

The recent progress in human genetics suggests major benefits in clinical p ractice, including psychiatry. This article introduces the research methodo logy used in psychiatric genetics and explains how it is applied for a bett er understanding of the challenges facing psychiatric genetics and the stra tegies being used to overcome them. We will review the evidence of genetic factors in psychiatric disorder etio logy as well as the specificity or non-specificity of their expression. We will discuss problems associated with the approximate nature of diagnostic methods, the incomplete penetrance and the genetic heterogeneity of psychia tric disorders, the presence of phenocopies and our uncertainty concerning the mode of inheritance of psychiatric disorders. Finally. we will provide an overview of the most promising results and set out priorities for future studies.