The great difficulty with psychosocial environmental factors and psychosocially mediated effects of physical environmental factors is their great complexity. They finally produce stimuli that act on an organism. The organism is characterized by psychobiological programming determined by genetic factors and by earlier environmental influences. The interaction between these factors causes the organism to react. In some cases the reaction manifests itself as a disease, in some as a psychosomatic symptom. The task is to identify critically important system components that are necessary or sufficient or contributory in causing disease or accelerating its course or triggering its symptoms. It is not just causation in the strict sense of the word; a broader concept is needed to identify these components so that something can be done about them.

Key terms health effect; stress