Observational · 2026
Who does not improve on anhedonia after ketamine? A small study of 34 inpatients
- Original title
- Clinical correlates of anhedonia non-response to ketamine in treatment-resistant depression.
- Authors
- Walaszek M, Cubała WJ, Kachlik Z, et al.
- Journal
- Journal of affective disorders, 2026
- Molecules
- Ketamine
- Conditions
- Treatment-resistant depression
- Participants
- 34
- Evidence grade
- Low
- Source
- Read the original paper
The question
Among hospital inpatients with hard-to-treat depression who received ketamine, which personal and clinical characteristics were linked to little or no improvement in anhedonia (the loss of pleasure or interest in things)?
What they did
Researchers looked back at records from two naturalistic observational registries covering 34 inpatients with treatment-resistant major depressive disorder. Over four weeks, patients received short-term ketamine added to their usual care, either intravenously (0.5 mg/kg) or by mouth (2.0-2.5 mg/kg). Anhedonia was measured with the Snaith-Hamilton Pleasure Scale, and patients were counted as responders if their score dropped by at least half. The two groups were then compared on social, demographic and clinical details.
What they found
16 of the patients (47.1%) did not reach the anhedonia response threshold. Most background characteristics did not differ between responders and non-responders. Non-responders had fewer lifetime depressive episodes, lower rates of past substance use disorder, and were more likely to be single. A statistical model combining these three factors was significant overall (p = 0.024). The split between intravenous and oral ketamine was similar in both groups (p = 0.68).
The fine print
This was a small, retrospective, exploratory analysis of 34 people with no placebo group and no randomization, so nothing here shows cause and effect. With so few patients, the differences found could easily be chance, and multiple characteristics were tested at once. Anhedonia response was defined by a single self-report scale over four weeks, with no longer-term follow-up reported. This summary is based on the abstract only.
What it means
About half of these inpatients did not show a large drop in anhedonia after four weeks of add-on ketamine, and a few background factors were loosely linked to non-response. The findings are preliminary and would need testing in larger, properly controlled studies before they could guide anyone’s care.
Evidence grade: Low. A small retrospective analysis of observational registry data with no control group and exploratory statistics, so it can only suggest associations.
This summary is based on the study’s published abstract.