Ketamine infusions administered intravenously 1 to 3 times per week are the quickest and most effective treatment for depression. Short-course ketamine medication is established treatment both for unipolar depression and depressive episodes of bipolar affective disorder. Ketamine is suitable for initiating the treatment for treatment-resistant depression, alleviation of suicidal tendencies, and treatment of depressive patients suffering from simultaneous pain. The safety of prolonged treatment with ketamine is not known to sufficient degree. However, even long periods (up to 1.5 years) of ketamine treatment have not been associated with adverse effects. It would be appropriate to use short-course ketamine treatment more often than is currently done.