Ketamine Infusions and Rapid Reduction of Suicidal and Depressive Symptoms in Major Depressive Episode: A Systematic Review and Meta-Analysis.

A systematic review and meta-analysis of 26 randomized clinical trials with 1,166 patients experiencing a major depressive episode found that intravenous ketamine infusions significantly reduce suicidal and depressive symptoms in the acute phase. A single ketamine infusion lowered suicidal symptoms at 24 hours and at 1 month, and repeated infusions produced similar reductions. Depressive symptoms decreased significantly from 4 hours through 1 week after a single infusion and after repeated infusions. Serious adverse events were unrelated to the interventions, and other side effects were transient. Longer-term outcomes remain unclear.

Study at a glance

Abstract

While intravenous ketamine is not approved by the US Food and Drug Administration, it is increasingly used with off-label indications as a novel treatment for suicidal and depressive symptoms. To systematically review and metasynthesize the efficacy and safety data for intravenous ketamine in treating major depressive episodes (MDEs). PubMed, PsycInfo, Cochrane Library, and Embase were systematically searched from database inception through November 7, 2025, with no language limits. Randomized clinical trials (RCTs) with (1) diagnosis of an MDE; (2) intervention and comparator groups consisting of intravenous ketamine and controls (eg, saline or midazolam); and (3) suicidal and depressive symptoms as efficacy outcomes were included. Hedges g standardized mean differences (SMDs) were used to analyze improvement in suicidal and depressive symptoms using random-effects models. Multiple subgroup analyses were also conducted. The main outcomes included the following: (1) changes in suicidal and depressive symptoms; (2) response and remission rates of depressive symptoms; and (3) safety measures (eg, adverse events and serious adverse events). A total of 26 RCTs comprising 1166 patients with an MDE (n = 626 receiving ketamine and n = 540 as control patients) were included. For suicidal symptoms, patients receiving a single ketamine infusion, compared with control patients, had significantly lower symptoms at 24 hours (SMD, -0.69 [95% CI, -0.98 to -0.40]) and at 1 month (SMD, -0.70 [95% CI, -1.17 to -0.24]). Those with repeated ketamine infusions showed a similar reduction of suicidal symptoms at the end of the treatment (SMD, -0.72 [95% CI, -1.00 to -0.43]). For depressive symptoms, significant reductions were shown at 4 hours (SMD, -1.74 [95% CI, -2.43 to -1.06]), 24 hours (SMD, -1.15 [95% CI, -1.58 to -0.72]), 3 days (SMD, -0.97 [95% CI, -1.73 to -0.20]), and 1 week (SMD, -0.89 [95% CI, -1.65 to -0.13]) after a single ketamine infusion and at the end of the treatment after repeated infusions (SMD, -0.81 [95% CI, -1.16 to -0.46]). Reported serious adverse events (eg, hospitalizations and deaths) were unrelated to the interventions, and other adverse events (eg, headache) were transient and resolved during the trials. The findings of this systematic review and meta-analysis suggest that single and repeated intravenous ketamine infusions are efficacious in reducing suicidal and depressive symptoms in patients with an MDE in the acute phase, while longer-term outcomes are not well established.