 Patients randomized to the experimental treatment receive intravenous infusions of racemic ketamine 0.5 mgkg, delivered over a period of forty minutes thrice weekly Monday, Wednesday, Friday. Patients in the control group receive ECT in line with standard procedures including anesthesia, muscle relaxation and oxygenation thrice weekly. ECT was chosen as the reference treatment as it is the most effective treatment for patients suffering from moderate to severe depression. 