[Familial aggregation of psychiatric disorders and the consequences for the psychiatric diagnosis].

Schizophrenic and affective disorders, anxiety disorders, and alcoholism show familial aggregation; the impact of familial aggregation on the classification and etiology of psychiatric disorders is discussed. Ideal diagnostic schedules should a) identify conditions with a substantially increased familial risk and b) reach diagnostic homogeneity in multiplex families. A review of the literature shows a) that age at onset, long-term course and comorbidity modify familial risks and should therefore be given more attention in diagnostic schedules and b) that the heterogeneity of disorders in multiplex families draws the validity of currently used diagnostic schedules into question. Against this background the hypothesis of "unitary psychosis" is discussed.