Effect of Lithium Versus Placebo in Adults With Treatment-Resistant Depression Who Are Receiving Ketamine

This is a randomized clinical trial in adults with Treatment-Resistant Depression. All participants will receive three intravenous (IV) Ketamine (KET) infusions over 7 days. Before receiving the first KET infusion, subjects will be randomized to 2 weeks of pre-KET treatment with either Lithium or matching placebo. Pre-treatment medications will then be continued in a double-blind manner during the acute phase administration of ketamine. Questionnaires will be administered at baseline, prior to each KET infusion, and at 40, 100, and 120 minutes after each infusion, and again at weekly intervals following the third (final) KET infusion for 4 weeks, using standardized rating scales. Those who achieve positive response (\>50% decrease in questionnaire total score from baseline) will be given 4 additional once-weekly KET infusions (same dose and infusion rate).