A 34-year-old woman is brought to the psychiatric clinic by her sister, who reports the patient has been increasingly withdrawn over the past 6 weeks. The patient describes pervasive sadness, anhedonia, insomnia with early morning awakening, a 12-pound weight loss, and psychomotor retardation. During the interview, she reveals she hears a voice telling her she is 'worthless and should disappear.' She reports that the voice started approximately 3 weeks after her mood began deteriorating and states she has never heard voices when she is feeling well. Her sister confirms that between depressive episodes, the patient functions at her baseline with no perceptual disturbances. Previous psychiatric history includes two prior major depressive episodes, one of which also involved auditory hallucinations that resolved completely with remission of the depressive episode. There is no history of manic or hypomanic episodes. Which of the following is the most accurate diagnosis?