Psychiatric genetics and psychiatric nosology

At the present time, family and twin data are used in psychiatry to test clinical concepts at issue, and, in particular, to validate or reject diagnostic classifications. The dichotomy between the schizophrenias and the effective disorders, as suggested by Kraepelin, has been supported by contemporary family and twin studies and also is corroborated by modern family and adoption studies. In the atypical psychoses it is demonstrated impressively how family data vary with different sampling procedures and diagnostic practices. In the affective disorders, the family findings at first favored the separation of unipolar and bipolar disorders but, subsequently, this concept was questioned and revised. Currently, psychiatric genetics attempts to contribute to the understanding of the affective disorders, in particular the depressions, by delineating subgroups and by looking for possible genetic relations between depression and frequently associated disorders, such as anxiety or anorexia.