If you are in crisis, call or text 988 (Suicide & Crisis Lifeline) in the United States, or go to your nearest emergency department. Ketamine therapy is not a substitute for emergency care.

Why Speed Is the Central Question

Conventional antidepressants typically take four to six weeks to show meaningful benefit. For someone experiencing active suicidal ideation, that delay is the entire clinical problem. Ketamine's most consistently replicated finding across two decades of research is not that it treats depression better than other drugs — it is that it works faster, sometimes within hours.

Two large meta-analyses published in 2025 and 2026 have now quantified that effect with far more precision than earlier single trials allowed.

The 2026 JAMA Psychiatry Meta-Analysis

Rhee and colleagues (JAMA Psychiatry, published online May 2026) pooled 26 randomized controlled trials involving 1,166 participants with a major depressive episode (626 assigned to ketamine, 540 to control conditions including saline and midazolam).

After a single infusion

  • Suicidal ideation: standardized mean difference (SMD) of −0.69 at 24 hours, still −0.70 at one month
  • Depressive symptoms: SMD −1.74 at 4 hours, −1.15 at 24 hours, −0.97 at 3 days, and −0.89 at one week

After repeated infusions

  • Suicidal ideation: SMD −0.72 at the end of the treatment course
  • Depressive symptoms: SMD −0.81 at the end of the treatment course

For context, an SMD of 0.5 is generally considered a moderate effect and 0.8 a large one. The 4-hour depression effect is among the largest short-term effect sizes reported for any psychiatric intervention.

The 2025 Meta-Analysis of 49 Trials

Feng and colleagues (Progress in Neuro-Psychopharmacology & Biological Psychiatry, January 2025) took a broader view, pooling 49 trials and 3,982 patients across psychiatric diagnoses rather than depression alone.

  • Single dose: SMD for suicidal ideation of −0.61 at 4 hours, peaking at −0.96 at 24 hours, and still −0.95 at one month
  • Repeated dosing: SMD −1.23 at the end of treatment and −1.01 at follow-up of one month or longer
  • Notably, the difference between single-dose and repeated-dose protocols was not statistically significant

That last point matters clinically. It suggests the anti-suicidal effect is largely front-loaded rather than accumulating steadily with each additional infusion — consistent with what real-world clinics report, where the largest symptom shifts tend to occur in the first two or three treatments.

Supporting Randomized Evidence

These meta-analyses build on individual trials that pointed the same direction. The French KETIS trial (Abbar et al., BMJ, 2022) randomized patients hospitalized with suicidal ideation to ketamine or placebo and found full remission of suicidal ideation on day 3 in 63.0% of the ketamine group versus 31.6% of the placebo group (odds ratio 3.7; 95% CI, 1.9 to 7.3). The effect was largest in the bipolar depression subgroup.

A 2024 meta-analysis in European Archives of Psychiatry and Clinical Neuroscience covering 13 trials and 1,109 patients found a more modest but still significant effect for racemic ketamine monotherapy on suicidal ideation (SMD −0.36; 95% CI, −0.71 to −0.01), a reminder that pooled estimates vary meaningfully with inclusion criteria.

What These Studies Do Not Establish

Honest interpretation requires naming the gaps:

  • Ideation is not behavior. Trials measure scores on suicidal ideation scales. They are not powered to detect reductions in suicide attempts or deaths, and no trial has demonstrated that ketamine reduces suicide mortality.
  • Blinding is imperfect. Ketamine produces noticeable dissociative effects, so participants often guess their assignment. This can inflate measured benefit — a limitation acknowledged across this literature.
  • Effects fade. A single infusion is a bridge, not a treatment plan. Without follow-on care, symptoms commonly return within days to weeks.
  • Trial populations are screened. Participants with active substance use, psychosis, or unstable medical conditions are typically excluded.

How This Is Used Clinically

The practical role that emerges from this evidence is a bridging one: rapid stabilization of acute suicidal ideation while slower-acting treatments — psychotherapy, medication adjustments, structured follow-up — are put in place. Research on that handoff is active, including trials pairing cognitive behavioral therapy with ketamine or esketamine specifically to extend the initial gains.

If you are evaluating treatment options, our guide to candidacy and screening outlines what a responsible clinic should assess before treatment, and you can find clinics by state to ask about crisis protocols and follow-up care directly.

Sources

  • Rhee TG, et al. Ketamine Infusions and Rapid Reduction of Suicidal and Depressive Symptoms in Major Depressive Episode: A Systematic Review and Meta-analysis. JAMA Psychiatry. Published online May 2026. doi:10.1001/jamapsychiatry.2026.0612
  • Feng W, et al. Efficacy of single and repeated ketamine administration for suicidal ideation in adults with psychiatric disorders: A meta-analysis. Prog Neuropsychopharmacol Biol Psychiatry. 2025. doi:10.1016/j.pnpbp.2024.111152
  • Abbar M, et al. Ketamine for the acute treatment of severe suicidal ideation: double blind, randomised placebo controlled trial. BMJ. 2022;376:e067194. doi:10.1136/bmj-2021-067194
  • Li J, et al. Efficacy of racemic ketamine or esketamine monotherapy for reducing suicidal ideation in uni- or bipolar depression: systematic review and meta-analysis. Eur Arch Psychiatry Clin Neurosci. 2024. doi:10.1007/s00406-024-01920-x