Twenty years ago, the biopsychosocial model was proposed by George Engel to be the new paradigm for medicine and psychiatry. The model assumed a hierarchical structure of the biological, psychological and social system and simple interactions between the participating systems. This article holds the thesis that the original biopsychosocial model cannot depict psychiatry's reality and problems. The clinical validity of the biopsychosocial model has to be questioned. It is argued that psychiatric interventions can only stimulate but not determine their target (...) systems, because intervention and outcome are only loosely coupled. Thus, psychiatric interventions have in principle limited ranges which differ according to the type of intervention and according to the system to be stimulated. Psychosocial interventions face far more obstacles to be overcome than psychopharmacogical therapy. (shrink)