PS222. Ketamine Exerts a Prolonged Reduction in Suicidal Ideation Independent of its Antidepressant Effects
Bibliographic record
Abstract
Abstract Background: Subanaesthetic doses of intravenous ketamine have been shown to elicit rapid reduction in depressive symptoms and severity of suicidal ideation (SI). However, the antidepressant properties of ketamine appear to be transient. Repeated ketamine infusions may prolong the antidepressant effect. The objective of this study was to determine whether ketamine could elicit decrease in SI even in patients who do not have a reduction in depressive symptoms with prolonged treatment. Methods: 19 patients with treatment-resistant major depressive disorder (MDD) completed a randomized controlled trial of ketamine. Patients received 7 intravenous ketamine infusions during the study, including a single infusion during the Phase 1 double-blind crossover with midazolam (used as an active placebo), and 6 ketamine infusions administered over a two-week period during Phase 2. The primary outcome measures were pre- and post-treatment changes in depressive symptoms (using the Montgomery-Asberg Depression Rating Scale [MADRS]) and suicidal ideation (using MADRS-SI scores). Results: Patients with a 50% decrease in total MADRS scores from pre- to post-treatment were considered ketamine responders. Responders (n = 10) had a larger reduction in MADRS scores (62%) compared to nonresponders (n = 9; 17%) (p<0.001). Both groups had significant reductions in MADRS-SI scores (responders -1.9, p<0.001; nonresponders -1.6, p<0.001) and the difference in the magnitude of change in MADRS-SI scores between groups was not statistically significant (p=0.44). Conclusions: Ketamine had a direct effect on lessening suicidal ideation even in patients who failed to show a reduction in depression severity with repeated infusions.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.006 | 0.002 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".