The incidence of depressive disorders is constantly growing. The biopsychosocial model considers sophisiticated psychosomatic and somatopsychic interrelationships and mental and somatic disorders. In clinical practice we deal with differential diagnosis within the depressive syndrome and have to decide between bipolar depression, schizophrenic depression, depression comorbid with somatic pathology, drug induced depression, as well as manifestation of personality pathology and character trait and a wide spectrum of reactive depression. All this mentioned above allow as to consider depression as an equivalent pathological state of a wide range of illnesses. This point of view builds a challenge for a new understanding of pathogenesis of depression that should find it’s proper place in the classification approach.