[Endophenotype--a new concept for biological characterization of psychiatric disorders].

In the field of psychiatric genetics, the concept of endophenotypes is presently receiving high popularity. Current difficulties in the search for susceptibility genes of complex diseases have been attributed to the etiological heterogeneity of the clinical, psychopathologically defined phenotype of the disease. Neurobiological correlates of the disease which are genetically influenced and stable over time are considered to be more promising targets of phenotypes. They are more directly influenced by gene effects and presumably defined by a genetic determination which is less complex than the phenotype of the disorder. The endophenotype strategy has already been successful in complex disorders of other areas in medicine, including alcoholism and late-onset Alzheimer's disease. For schizophrenia, a series of endophenotypes for molecular/genetic investigation has been suggested, but the concept "endophenotype" also provides a basis for biological classification of mental disorders.