 A half century ago, diagnosed depression was either endogenous (melancholic), considered a biological condition, or reactive (neurotic), a reaction to stressful events.Debate has persisted for most of the 20th century over whether a unitary or binary model of depression is a truer reflection of the syndrome; in the former, there is a continuum of depression ranked only by severity and the result of a "psychobiological final common pathway", whereas the latter conceptualizes a distinction between biological and reactive depressive syndromes.The publishing of DSM-III saw the unitarian model gain a more universal acceptance.