summary
background In recent years quantitative genetic research has addressed all the major psychiatric disorders. In order to interpret the results of this type of research one needs to be aware of its potential and its limitations.
aim To discuss the basic concepts and the main results of quantitative genetic research and to consider how this can help us to better understand the aetiology of psychiatric disorders.
methods Using Medline (1990-February 2006) we reviewed the literature on the subject of quantitative genetic and psychiatric disorders. In addition we studied the standard books on the subject.
results A fairly large number of psychiatric disorders, namely about 30 to 85%, can be inherited. In addition, the non-shared environment has a considerable influence on the phenotype. The influence of the shared environment seems to have only a limited influence or it is totally absent. The results of quantitative genetic research are specific to a particular time or environment and therefore may not be applicable to other populations. There may be a correlation or interaction between genetic factors and the environment while the phenotype is being formed. However, because of the analytical methods used, this is only partly visible in the results.
conclusion Quantitative genetic research has made an impressive contribution to our knowledge about the heritability of psychiatric disorders. By definition quantitative genetic research always provides information about environmental influences. [