<qa>  What is fludrocortisone vs. spironolacThe proposed research aims to compare the onset of action and the efficacy of fludrocortisone, a mineralocorticoid receptor agonist vs. spironolactone, a mineralocorticoid antagonist, vs. placebo as augmentation to a selective serotonin reuptake inhibitor SSRI in 65 inpatients with severe depression. The study will also explore the utility of the hypothalamic-pituitary-adrenal HPA axis in predicting treatment response. The study will be a 5-week randomized and double-blind trial of fludrocortisone vs. spironolactone vs. placebo during three years. 