Observational · 2026
Blood inflammation marker linked to esketamine response in 16 people with hard-to-treat depression
- Original title
- Higher Neutrophil-to-Lymphocyte Ratio Is Associated With Better Response to Esketamine in Treatment-Resistant Depression: A Post Hoc Exploratory Analysis of Real-World Data.
- Authors
- Carminati M, Tondello M, Morana C, et al.
- Journal
- Journal of clinical psychopharmacology, 2026
- Molecules
- Esketamine
- Conditions
- Treatment-resistant depression
- Participants
- 16
- Evidence grade
- Very low
- Source
- Read the original paper
The question
Does a simple blood marker of inflammation, measured before treatment, predict who responds to nasal esketamine for depression that has not improved with other treatments?
What they did
Researchers reviewed records from patients at a mood disorders unit in Milan, Italy, who were given intranasal esketamine alongside their usual antidepressant treatment. Before treatment started, each patient had a routine blood test, from which the team calculated the neutrophil-to-lymphocyte ratio (NLR) — a rough measure of how much inflammation and immune imbalance is present in the body. Blood was drawn 1 to 7 days before the first dose. Clinicians rated overall improvement after 7 months using a standard global rating scale, splitting patients into responders and non-responders.
What they found
The final sample was 16 patients: 8 responders and 8 non-responders. Responders had a higher average baseline NLR than non-responders (1.81±0.81 versus 1.23±0.29). After statistically adjusting for age, the difference between the two groups was significant (P=0.003).
The fine print
With only 16 people, results like this can easily be a fluke, and the study was retrospective, with no control group, no randomization and no blinding. Response was judged by a clinician’s overall impression rather than a detailed symptom scale. The abstract describes the outcome at 7 months in the methods but 6 months in the conclusion, an inconsistency that is not explained. This summary is based on the abstract alone.
What it means
This small, exploratory analysis raises the possibility that a person’s baseline inflammation might relate to how well esketamine works, but the study is far too small to guide any clinical decision.
Evidence grade: Very low. A retrospective look back at records from only 16 patients, with no control group and no randomization, so the finding is preliminary at best.
This summary is based on the study’s published abstract.