Risk of relapse into an affective episode was high in the months immediately after recovery from a major depressive disorder (MDD) in 141 subjects with nonbipolar depression, without a preexisting dysthymic disorder. The probability of relapse then declined steadily during the duration of the follow-up (median follow-up, 62 weeks from recovery). In patients entering the study during their first affective episode, the Research Diagnostic Criteria secondary subtype of MDD and an older age of onset predicted a significantly greater likelihood of relapse. Three or more prior episodes of depression predicted a significantly shorter time to the first and second prospectively observed relapses and, thus, a significantly greater likelihood of subsequent multiple affective episodes.
Keller MB, Lavori PW, Lewis CE, Klerman GL. Predictors of Relapse in Major Depressive Disorder. JAMA. 1983;250(24):3299-3304. doi:10.1001/jama.1983.03340240025024