" Depression cannot be described in terms of 'normal psychology'; only the somewhat general term of "depressedness" can be understood in the sense of this anergic (i.e. incomprehensible by normal mentality) mood.
In mild cases, the patients appear almost more apathetic than actually depressive; in severe cases, however, deep suffering develops. "

― , Classification of Endogenous Psychoses and Their Differentiated Etiology