The aim of the work was to review the literature on the problem of assessing the severity of depression in the light of changes in the systematization of mental disorders. The relevance of the correct assessment of mental disorders on the example of depressive disorder is substantiated. New approaches to determining the severity of disorders in DSM-5 are presented, their variability is noted. The influence of the depression severity on the choice of therapy, preference for psychopharmacotherapy or psychotherapy is analyzed. There was made a conclusion about the prospect of assessing the severity of depression on the basis of dimensions.