Other · 2026
Which patients respond best to ketamine for suicidal thoughts? A post-hoc analysis of 67 people
- Original title
- Using Classification and Regression Tree Modeling to Investigate the Effects of Subanesthetic Ketamine Infusion on Remission of Suicidal Symptoms.
- Authors
- Wu PC, Lin WC, Su TP, et al.
- Journal
- Pharmacopsychiatry, 2026
- Molecules
- Ketamine
- Conditions
- Treatment-resistant depression, Suicidal ideation
- Participants
- 67
- Evidence grade
- Low
- Source
- Read the original paper
The question
Can a combination of simple baseline characteristics predict who will see their suicidal thoughts ease after a single ketamine infusion?
What they did
Researchers re-analyzed data from their earlier randomized placebo-controlled and open-label studies. The pooled sample was 67 people with treatment-resistant depression (depression that had not responded to previous treatments) and prominent suicidal thinking, all of whom received one ketamine infusion at 0.5 mg/kg. They used a statistical method called a classification and regression tree, which splits people into groups based on combinations of baseline features, to see which combinations best predicted an antisuicidal response.
What they found
No single characteristic predicted response well on its own. Combinations did better: mild or moderate depression severity, a shorter current depressive episode, no more than four previous failed antidepressant trials, low or moderate current suicide risk, and a past suicide attempt together predicted both rapid and sustained reductions in suicidal symptoms. The abstract reports no response rates, effect sizes or accuracy figures for the model.
The fine print
This was a post-hoc analysis, meaning the question was asked after the original trials ended, so the findings are exploratory rather than confirmed. The sample of 67 people is small for building a prediction model, and it mixed placebo-controlled and open-label data. The model was not tested in a separate group of patients, so it may not hold up elsewhere. The abstract gives no numbers for how accurate the predictions were, and this summary is based on the abstract only.
What it means
Combining several baseline clinical details may help estimate who is more likely to see suicidal thoughts ease after a ketamine infusion, but these patterns are preliminary and need testing in new, independent groups of patients.
Evidence grade: Low. A post-hoc analysis that pooled data from an earlier placebo-controlled trial and an open-label trial in a small sample, with no separate group to test the prediction model.
This summary is based on the study’s published abstract.