OBSERVEMDD0001 (A prospective, longitudinal, observational study to evaluate potential predictors of relapse in subjects with major depressive disorder who have responded to antidepressant treatment) Investigators : Jeffrey I. Bennett, MD (Faculty, Adult Division) Obiora Onwuameze, MD (Faculty, Adult Division) Vinod Alluri, MD (Faculty, Adult Division) Eric Black, MD (Faculty, Adult Division) Santosh Shrestha, MD (Faculty, Adult Division) Arindam Chakrabarty, MD (Resident) This multisite, industry sponsored study investigates measurable parameters predicting relapse in recurrent Major