An episode of depression lasting two or more weeks without an intervening episode of mania. The disease is MONDO_0002009 (major depressive disorder). Also known as: MDD, major depression, major depressive disorder and accelerated response to antidepressant drug treatment, major depressive disorder, response to citalopram therapy in, recurrent major depression, single major depressive episode, unipolar depression, unipolar depression, susceptibility to.