Ketamine-assisted psychotherapy for posttraumatic stress disorder: a systematic review and individual participant data meta-analysis of predictors of treatment effects.
Judith Rohde, Tyler M Moore, Kathryn Walker, Shobi S Ahmed, Henry A MacConnel, Martin Krsak, Scott Shannon, Vivian W. L. Tsang, Shannon Dames, Marco Buchmann, Birgit Kleim, Erich Seifritz, Sebastian Olbrich, Georgios Schoretsanitis
Psychotherapy and Psychosomatics June 19, 2026 DOI: 10.1159/000553144 (opens in new tab)
Study at a glance
AI-extracted from the abstract| Characteristics | Systematic review and individual participant data meta-analysis Peer reviewed |
|---|---|
| Sample size | 533 |
| Population | Adults with PTSD |
| Interventions | Ketamine Psychotherapy |
| Topics | Esketamine Ketamine Psychedelic-assisted therapy PTSD |
| Key findings | Higher baseline PTSD severity was the most robust predictor of symptom reduction after combined ketamine and psychotherapy, while more sessions and shorter treatment duration were also associated with greater improvement. |
Abstract
Ketamine combined with psychotherapy has shown promise in treating posttraumatic stress disorder (PTSD), but predictors of clinical benefit remain unclear. In this systematic review and individual participant data meta-analysis (IPDMA), we examined patient- and treatment-level predictors of PTSD symptom change after combined treatment. Eligible studies combined ketamine with psychotherapy in adults with PTSD. The primary outcome was PTSD symptom change on the PTSD Checklist for DSM-5 (PCL-5). We fit linear mixed-effects models with a random intercept for study and fixed effects for age, sex, baseline PCL-5, number of ketamine sessions, number of psychotherapy sessions, administration route, and treatment duration. Sex-stratified analyses and a quality-restricted sensitivity analysis were conducted. Twelve studies (533 participants) were included; nine were of poor quality. Greater improvement was associated with more psychotherapy (β = 1.03 per session) and more ketamine sessions (β = 1.15 per session), higher baseline symptom severity (β = 0.50 per PCL-5 point), and shorter treatment duration (β = -0.58 per week). Between-study heterogeneity was non-trivial (ICC ≈ 0.15). In sex-stratified models, number of psychotherapy sessions, baseline severity, and shorter treatment duration remained associated with improvement in both sexes. In the sensitivity analysis (n = 63), baseline severity was the only significant predictor of treatment outcome. Higher baseline PTSD severity was the most robust predictor of symptom reduction. Session intensity and treatment timing may matter, but associations should be interpreted cautiously given the predominance of poor-quality studies and require replication in prospective trials with standardized protocols and longer follow-up.
In the evidence
This study is part of the evidence base for 2 syntheses in the library. Here is how each one recorded it.
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Greater PTSD symptom improvement after combined ketamine and psychotherapy was associated with more psychotherapy sessions, more ketamine sessions, higher baseline severity, and shorter treatment duration; nine of twelve included studies were of poor quality.
Synthesized
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Higher baseline PTSD severity was the most robust predictor of symptom reduction after combined ketamine and psychotherapy, with more sessions and shorter treatment duration also associated with greater improvement.
Synthesized
Comparable studies
Other systematic reviews and meta-analyses on ketamine and psychedelic-assisted therapy, most cited first.