Depression as an affect or feeling tone is a ubiquitous and universal condition which as a human experience extends on a continuum from normal mood swings to a pathological state. Thus, depression as a word can be used to describe: (i) an affect which is a subjective feeling tone of short duration; or (ii) a mood, which is a state sustained over a longer period of time; or (iii) an emotion, which is comprised of the feeling tones along with objective indications; or (iv) a disorder which has characteristic symptom clusters, complexes, or configurations. (2, p330)