[Schizophrenia. Current biological theories on the etiology].

Recent biological research on the aetiology of schizophrenia is reviewed. High risk studies, family studies, twin studies, adoption studies, molecular genetics and studies on the pre- and perinatal environmental factors are reviewed and it is concluded that the diathesis-stress-model is still the predominant aetiological hypothesis, although the biological environmental factors seem to play a minor role. It is also concluded that the international diagnostic systems although valid for clinical diagnostic purposes are insufficient for the aetiological research of schizophrenia. With a view to finding aetiologically valid phenotypes, future research areas with the aim of broadening the phenotype or finding endophenotypes are discussed.