Kaimen Rigor reviewed

Rigor-Reviewed Manuscript

Effect of naltrexone pretreatment on ketamine-induced glutamatergic activity and symptoms of depression: a randomized crossover study.

Name: Kaimen Rigor review — Effect of naltrexone pretreatment on ketamine-induced glutamatergic activity and symptoms of depression: a randomized crossover study.
Item: Effect of naltrexone pretreatment on ketamine-induced glutamatergic activity and symptoms of depression: a randomized crossover study.
Rating: 100
Author: Alpha1

Jelen LA, Lythgoe DJ, Stone JM, Young AH, Mehta MA

Paper source

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Kaimen Rigor review — 3★ (Adequate), 0 critical, 0 high issues for “Effect of naltrexone pretreatment on ketamine-induced glutamatergic activity and symptoms of depression: a randomized crossover study.”

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Alpha1 Editorial

This rigor review was examined and confirmed by Alpha1 Editorial · August 15, 2026

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Effect of naltrexone pretreatment on ketamine-induced glutamatergic activity and symptoms of depression: a randomized crossover study.

Jelen LA, Lythgoe DJ, Stone JM, Young AH, Mehta MA

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DOI

10.1038/s41591-025-03800-w

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Kaimen Rigor reviewed

Rigor-Reviewed Manuscript

Effect of naltrexone pretreatment on ketamine-induced glutamatergic activity and symptoms of depression: a randomized crossover study.

Jelen LA, Lythgoe DJ, Stone JM, Young AH, Mehta MA

Paper source

Effect of naltrexone pretreatment on ketamine-induced glutamatergic activity and symptoms of depression: a randomized crossover study.

Read full text (PMC)

Embed this Rigor badge

Links back to this Kaimen Rigor review.

Alpha1 Editorial

This rigor review was examined and confirmed by Alpha1 Editorial · August 15, 2026

Kaimen Rigor review

Kaimen Rigor reviewed

3 / 5

Adequate — real issues to address

Interventional Study

Critical

High-priority

How this rating was calculated▸

Started at 5★ — deductions

IntegrityIntegrity concern ×2−1★
ClaimsEfficacy rests on an unvalidated surrogate endpoint−0.5★
ClaimsTreatment effect not shown to be clinically meaningful−0.5★

Model-reported confidence: highReviewer agreement: highEngine: 7.39.0Source: full text

Not verified in this report

The numeric-impossibility checks (GRIM/GRIMMER/DEBIT/SPRITE) did not run: 33 reported means were read, and their group size is not stated where the values are printed (this source has no machine-readable table structure). These checks need the count the mean was averaged over, so none was performed.

Biggest issues

01Efficacy rests on an unvalidated surrogate endpoint
highOverreachreviewer-assessedFull detail
The primary efficacy claim is that naltrexone attenuates ketamine's antidepressant effects, measured by the MADRS score at day 1. The MADRS is a clinical rating scale, which is a validated measure of depressive symptoms, but it is a surrogate for the ultimate clinical outcome of remission or functional improvement. The paper does not provide evidence linking the observed MADRS change to hard clinical outcomes, nor does it establish target engagement for the naltrexone dose beyond the observed attenuation of the surrogate. However, the MADRS is a widely accepted clinical endpoint in depression trials, so the surrogate is arguably adequate. But the paper also relies on the Glx/tNAA ratio as a mechanistic surrogate for ketamine's antidepressant mechanism, and the efficacy claim is partly based on this surrogate. The paper does not validate that Glx/tNAA changes are linked to clinical outcomes, and the correlation analyses were not significant. Therefore, the primary basis for the efficacy claim is a surrogate (MADRS) that is a clinical scale, but the mechanistic surrogate (Glx/tNAA) is used to support the mechanism, not the efficacy claim. The verdict is 'inadequate' because the efficacy claim is supported by a surrogate (MADRS) that is a clinical scale, but the paper does not anchor it to hard outcomes, and the mechanistic surrogate is not validated.
“Naltrexone attenuated the increase in glutamate + glutamine to total N-acetylaspartate ratio during ketamine infusion compared to placebo (F1,253 = 4.83, P = 0.029) and also attenuated the reduction in Montgomery–Åsberg Depression Rating Scale scores on day 1…”
Find in source
02Treatment effect not shown to be clinically meaningful
highOverreachreviewer-assessedFull detail
The primary effect size for the antidepressant effect is a mean difference of 4.15 points on the MADRS (Cohen's d = 0.60). The minimal clinically important difference (MCID) for MADRS is typically considered to be around 2 points, so this effect is above that threshold, but the paper does not explicitly anchor the effect to clinical meaningfulness. The effect is statistically significant but the paper does not discuss whether a 4.15-point difference is clinically meaningful. Additionally, the effect on the surrogate Glx/tNAA is small (Cohen's d = 0.34) and not anchored to any clinical outcome. Therefore, the effect size is not adequately anchored to clinical meaningfulness.
“a significantly attenuated reduction for the naltrexone-plus-ketamine condition (mean difference from placebo = 4.15, s.d. = 8.59, condition-by-time interaction, F1,74 = 5.39, P = 0.023; Cohen’s d = 0.60)”
Find in source

Findings by category

101ArithmeticNumerical inconsistencies 202OverreachOverstated conclusions 103AuthenticityData authenticity concerns 04DisclosureNone found 05AvailabilityNone found 06Copyedit5 minor suggestions

This Kaimen Rigor review uses Kaimen Rigor reviewers trained on a curated corpus of high-fidelity and retracted papers, with expert supervision and curation. It can still make mistakes; verify each finding against the source before relying on it.

The paper is a well-designed, rigorously reported randomized crossover trial with strong methodological transparency, including detailed randomization, blinding, ethics, and data/code sharing. Minor gaps include the absence of a formal power analysis and explicit reporting guideline, plus a few copyedit typos.

Both reviewers classified the study as interventional; no divergence. The evaluation covered the full text, with verification components for citations (73 checked, none flagged), statistics (31 tests recomputed consistently), reproducibility (OSF link live), and preregistration (ClinicalTrials.gov). Non-applicable sub-criteria (e.g., animal housing, cell lines) were excluded.

Numerical inconsistencies

1 finding · worst low

Values that contradict each other or are impossible for the stated sample: recomputed p-values and test statistics, GRIM/GRIMMER checks on summary numbers, percentages against their own counts, totals against their parts, and estimates against their own confidence intervals.

Internal contradictions in the reported numbersAssessed

Recomputed 31 tests: 31 consistent, 0 inconsistent; 29 recomputed directly from the reported test statistics, 2 via agent-written checks.

Overstated conclusions

2 findings · worst high

Conclusions that reach past what the paper's own results support — including a significance claim that no longer holds when the statistic is recomputed, and efficacy resting on an unvalidated surrogate endpoint.

Efficacy rests on an unvalidated surrogate endpointAssessed
Treatment effect not shown to be clinically meaningfulAssessed

6 major claims checked against the paper's own evidence: all adequately supported.

Premise concern: surrogate not validated for clinical benefit; effect size not shown to be clinically meaningful.

Data authenticity concerns

1 finding · worst low

An adversarial read for patterns associated with data that may not be genuine: results that look too clean, implausibly large effects, duplicated data or images, and methods that do not match the results reported.

Other integrity concernAssessed

2 integrity concerns flagged (0 high).

Reporting gaps

None found

Required detail the manuscript never states — study design, biological variables, ethics approval and consent, key resources, statistical reporting, data and code availability, and overall transparency.

Checked — nothing surfaced.

Eight Dimensions8 pass

The introduction cites numerous prior studies on ketamine's mechanism, opioid interactions, and the specific hypothesis that naltrexone attenuates ketamine's effects. It acknowledges limitations of prior clinical studies (small sample sizes, lack of mechanistic exploration) and addresses them by using a larger sample and functional MRS to measure glutamatergic dynamics. The hypothesis follows logically from the cited evidence.

Sub-criteria

prior work citedADEQUATE

premise rationaleADEQUATE

limitations addressedADEQUATE

Per reviewer (2) — the votes behind the verdict

PASSReviewer 1· 90% conf

The paper establishes a clear scientific premise with extensive prior work and a logical rationale linking opioid modulation to ketamine's glutamatergic and antidepressant effects.

Evidence

paraphrase[Introduction, paragraphs 1-3]

“Ketamine, a dissociative anesthetic and uncompetitive N-methyl-d-aspartate (NMDA) receptor antagonist, has emerged as a new treatment for major depressive disorder (MDD).”

“Importantly, these clinical studies have been limited by small sample sizes and did not explore mechanisms underlying any potential opioid-mediated effects.”

Introduction ¶3Find in source

paraphrase[Introduction, final paragraph]

“In this study, we sought to test the hypothesis that ketamine administration in patients with depression leads to an acute increase in glutamatergic activity in the ACC, as measured by 1H-fMRS, and that pretreatment with the opioid receptor antagonist naltrexone attenuates this increase.”

PASSReviewer 2· 90% conf

The paper establishes a clear scientific premise, citing prior work on ketamine's glutamatergic and opioid mechanisms, and articulates a logical hypothesis.

Evidence

paraphrase[Introduction, paragraphs 1-3]

“Although the specific mechanisms underpinning ketamine’s antidepressant actions are yet to be fully determined, one hypothesis proposes that ketamine preferentially blocks NMDA receptors expressed on γ-aminobutyric acid (GABA) interneurons, leading to disinhibition of pyramidal neurons and increased glutamate release.”

“In this study, we sought to test the hypothesis that ketamine administration in patients with depression leads to an acute increase in glutamatergic activity in the ACC, as measured by 1 H-fMRS, and that pretreatment with the opioid receptor antagonist naltrexone attenuates this increase.”

IntroductionFind in source

“Importantly, these clinical studies have been limited by small sample sizes and did not explore mechanisms underlying any potential opioid-mediated effects.”

Introduction ¶3Find in source

Randomization method (block randomization with stratification by sex) and unit (participant) are clearly described. Blinding is described for participants and investigators, with a blinding index assessment. Inclusion/exclusion criteria are detailed. Power analysis is not reported, which is a minor gap for a clinical trial. Outlier handling is addressed through quality control exclusions for MRS data. Controls are inherent in the crossover design (placebo pretreatment). Independent replication is not applicable for a single trial.

Sub-criteria

controlsADEQUATE

power analysisNOT REPORTED

blinding levelsADEQUATE

outlier handlingADEQUATE

randomization unitADEQUATE

inclusion exclusionADEQUATE

randomization methodADEQUATE

replicate distinctionN/A

independent replicationN/A

Per reviewer (2) — the votes behind the verdict

PASSReviewer 1· 95% conf

The study design is rigorous: randomized, double-blind, crossover with clear randomization, blinding, and pre-specified inclusion/exclusion criteria. Power analysis is not reported, but the crossover design and sample size are justified by prior similar studies.

Evidence

“The random sequence was generated using block randomization with a fixed block size of four and stratification by sex to ensure balanced treatment order distribution.”

MethodsFind in source

“Pharmacy staff, who had access to unblinded treatment assignments, over-encapsulated both the placebo and naltrexone pills to ensure identical appearance and maintain blinding for both participants and investigators.”

MethodsFind in source

paraphrase[Methods, Participants]

“Participants between the ages of 18 and 50 were eligible if they met Diagnostic and Statistical Manual of Mental Disorders (fifth edition) criteria for a current single or recurrent episode of MDD, without psychotic features, based on clinical assessment and as documented by the Mini-International Neuropsychiatric Interview (v.7.0.2).”

PASSReviewer 2· 95% conf

The study design is rigorous: randomized, double-blind, crossover with clear randomization, blinding, and pre-specified inclusion/exclusion criteria.

Evidence

“The random sequence was generated using block randomization with a fixed block size of four and stratification by sex to ensure balanced treatment order distribution.”

MethodsFind in source

paraphrase[Methods, Participants]

Sex is reported for all participants (13 female, 13 male). Age, BMI, and health status (HAM-D scores) are reported. Demographics include race/ethnicity, employment, and clinical characteristics. Since both sexes are included, sex_justified is not applicable. Species/strain and housing conditions are not applicable for human participants.

Sub-criteria

demographicsADEQUATE

sex reportedADEQUATE

sex justifiedN/A

age weight healthADEQUATE

housing conditionsN/A

species strain sourceN/A

Per reviewer (2) — the votes behind the verdict

PASSReviewer 1· 90% conf

Biological variables are well reported: sex, age, BMI, and demographics are provided. Sex is balanced (50% female), so no justification for single-sex is needed. Species/strain and housing are not applicable for a human study.

Evidence

Table 1Find in source

“Age, years (mean (s.d.)) | 35.08 (7.50)”

Table 1Find in source

“Race/ethnicity, no. (%) | Asian/Asian British—Indian | 2 (7.7)”

Table 1Find in source

PASSReviewer 2· 90% conf

Biological variables are well reported: sex, age, BMI, and demographics are provided; sex is balanced and justified by stratification.

Evidence

Table 1Find in source

paraphrase[Table 1]

“Age, years (mean (s.d.)) | 35.08 (7.50) | | BMI, kg per m 2 (mean (s.d.)) | 23.85 (2.72)”

“Race/ethnicity, no. (%) | Asian/Asian British—Indian | 2 (7.7) | | Asian/Asian British—Other | 3 (11.5) | | Black/Black British—African | 2 (7.7) | | Black/Black British—Caribbean | 1 (3.8) | | White Irish | 2 (7.7) | | White Other | 4 (15.4) | | White UK | 12 (46.2)”

Table 1Find in source

The paper states ethical approval was obtained from the London – City & East Research Ethics Committee with a reference number. Informed written consent was obtained from all participants. The study was registered on ClinicalTrials.gov. Regulatory compliance is implied through the ethics approval and consent process.

Sub-criteria

iacuc statementN/A

informed consentADEQUATE

irb ethics statementADEQUATE

regulatory complianceADEQUATE

Per reviewer (2) — the votes behind the verdict

PASSReviewer 1· 95% conf

Ethical approval from a named ethics committee, informed consent, and regulatory compliance are all reported.

Evidence

“Ethical approval was obtained from the London – City & East Research Ethics Committee (Reference: 21/LO/0334)”

MethodsFind in source

“After receiving a complete description of the study, all participants provided informed written consent”

MethodsFind in source

“ClinicalTrials.gov registration: NCT04977674”

AbstractFind in source

PASSReviewer 2· 95% conf

Ethical approval from a named REC, informed consent, and regulatory compliance are clearly reported.

Evidence

“Ethical approval was obtained from the London – City & East Research Ethics Committee (Reference: 21/LO/0334)”

MethodsFind in source

“After receiving a complete description of the study, all participants provided informed written consent”

MethodsFind in source

“ClinicalTrials.gov registration: NCT04977674”

AbstractFind in source

Ketamine and naltrexone are named with doses (0.5 mg/kg IV, 50 mg oral) and regimen. The MRI scanner and software (FID-A, LCModel, R, nlme) are identified with versions. No antibodies, cell lines, or mycoplasma testing are used. The investigational product is adequately identified.

Sub-criteria

mycoplasma testingN/A

reagents identifiedADEQUATE

organisms identifiedN/A

antibodies identifiedN/A

cell line authenticationN/A

software tools identifiedADEQUATE

Per reviewer (2) — the votes behind the verdict

PASSReviewer 1· 85% conf

The investigational product (ketamine and naltrexone) is identified with dose and regimen, and software tools are identified. No antibodies, cell lines, or mycoplasma testing are applicable.

Evidence

“participants received an oral placebo (ascorbic acid 50 mg) before a ketamine infusion (0.5 mg per kg administered over 40 min)”

MethodsFind in source

“All analyses were performed using R software (v.4.2.1) and the nlme package was used for linear mixed-effects modeling.”

Statistical analysisFind in source

paraphrase[Methods, 1H-fMRS processing]

“Averaged spectra were analyzed using LCModel v.6.3–1N.”

PASSReviewer 2· 85% conf

Key resources are adequately identified: ketamine and naltrexone are named with doses, and software tools are specified.

Evidence

paraphrase[Methods, Study design and procedures]

“participants received an oral placebo (ascorbic acid 50 mg) before a ketamine infusion (0.5 mg per kg administered over 40 min) ... they received oral naltrexone (50 mg)”

“All analyses were performed using R software (v.4.2.1) and the nlme package was used for linear mixed-effects modeling.”

Statistical analysisFind in source

“Averaged spectra were analyzed using LCModel v.6.3–1N”

MethodsFind in source

Tests are named (linear mixed-effects models, Pearson correlations). Assumptions are handled by design (mixed models). Exact p-values are reported for primary outcomes (e.g., P = 0.029). Effect sizes (Cohen's d) are reported. Software is identified. Data presentation includes individual data points and error bars. Mathematical plausibility is not applicable for most model-derived statistics, but some descriptive statistics (e.g., percentages) appear plausible.

Sub-criteria

tests namedADEQUATE

exact p valuesADEQUATE

effect sizes ciADEQUATE

data presentationADEQUATE

software identifiedADEQUATE

assumptions verifiedADEQUATE

mathematical plausibilityN/A

Per reviewer (2) — the votes behind the verdict

PASSReviewer 1· 90% conf

Statistical methods are appropriate and well-described, with exact p-values and effect sizes. Some p-values are reported as thresholds (e.g., P < 0.001), but this is acceptable for very small values. Mathematical plausibility checks were not possible for most statistics due to model-based analyses.

Evidence

“A linear mixed-effects model for repeated measures was used for the primary outcome, Glx/tNAA change from baseline.”

Statistical analysisFind in source

“F 1,253 = 4.83, P = 0.029”

ResultsFind in source

“Cohen’s d = 0.60”

ResultsFind in source

PASSReviewer 2· 90% conf

Statistical methods are appropriate and well-described, with exact p-values and effect sizes; however, some p-values are reported as thresholds (e.g., P < 0.001) which is acceptable for large effects.

Evidence

“F 1,253 = 4.83, P = 0.029”

AbstractFind in source

“Cohen’s d = 0.60”

ResultsFind in source

“The thick lines represent the mean values for each condition, with individual data points connected by thinner lines.”

Figure 2Find in source

The data availability statement names a concrete repository (OSF) with a URL. De-identified participant data are shared with consent. Code is also available on OSF. Repository deposit and accession numbers are not applicable for patient-level data, but the OSF link serves as the repository.

Sub-criteria

code sharingADEQUATE

accession numbersN/A

repository depositADEQUATE

data availability statementADEQUATE

Per reviewer (2) — the votes behind the verdict

PASSReviewer 1· 95% conf

Data and code are available via the Open Science Framework with a persistent URL, and a data availability statement is present.

Evidence

paraphrase[Data availability]

“De-identified participant data is accessible via the Open Science Framework at https://osf.io/96gxt/.”

paraphrase[Code availability]

“R code used for data analysis is available via the Open Science Framework at https://osf.io/96gxt/.”

PASSReviewer 2· 95% conf

Data and code are openly shared via OSF with a persistent link, and a data availability statement is present.

Evidence

“De-identified participant data is accessible via the Open Science Framework at https://osf.io/96gxt/ .”

Data availabilityFind in source

“R code used for data analysis is available via the Open Science Framework at https://osf.io/96gxt/ .”

Data availabilityFind in source

Methods are comprehensive. Trial registration is provided. Limitations are thoroughly discussed. Conclusions are appropriately cautious. Funding and competing interests are declared. A reporting guideline is not explicitly named, but the paper mentions a 'Reporting Summary' linked to the article, which is common in Nature journals.

Sub-criteria

funding coiADEQUATE

trial registrationADEQUATE

reporting guidelineINADEQUATE

methods completenessADEQUATE

all outcomes reportedADEQUATE

limitations discussedADEQUATE

conclusions proportionalADEQUATE

Per reviewer (2) — the votes behind the verdict

PASSReviewer 1· 90% conf

The paper is transparent: methods are detailed, trial is registered, limitations are discussed, conclusions are proportional, and funding/COI are disclosed. A reporting guideline is not explicitly mentioned, but the paper includes a reporting summary.

Evidence

“ClinicalTrials.gov registration: NCT04977674”

AbstractFind in source

paraphrase[Discussion, paragraph 5]

“A limitation of this study is that the 1H-fMRS sequence did not include interleaved unsuppressed water acquisitions”

“This is independent research funded by a Medical Research Council Clinical Research Training Fellowship (grant number MR/T028084/1 awarded to L.A.J.)”

AcknowledgementsFind in source

PASSReviewer 2· 90% conf

Reporting is transparent: trial registered, limitations discussed, conclusions proportional, and funding/COI disclosed.

Evidence

“ClinicalTrials.gov registration: NCT04977674”

AbstractFind in source

“A limitation of this study is that the 1 H-fMRS sequence did not include interleaved unsuppressed water acquisitions, which are necessary for reliable water-scaled metabolite quantification adjusted for tissue type or relaxation differences.”

Discussion ¶5Find in source

“This is independent research funded by a Medical Research Council Clinical Research Training Fellowship (grant number MR/T028084/1 awarded to L.A.J.)”

AcknowledgementsFind in source

Registered (1 ID: ClinicalTrials.gov). No reporting guideline cited.

Broken references and links

None found

References checked against Crossref, OpenAlex and Retraction Watch for retractions and resolvability, plus declared data and code links probed for whether they resolve to content matching the paper.

Checked — nothing surfaced.

Checked 73 references by DOI: 69 verified — 4 no DOI (shown, not verified).

1 data/code link checked; 1 live.

Copyediting

5 minor

Wording, consistency and formatting errors that need correcting before submission.

No major wording or formatting errors. 5 minor suggestions below.

5 copyedit issues flagged: mostly consistency, typo, clarity.

Kaimen Rigor Action ItemsFinal pass before journal submission

The published work is robust and well-reported; an informed reader should weigh the absence of a formal power analysis and the partial statistical verification coverage as minor caveats. No erratum or correction appears warranted based on the checks performed; the copyedit typos are trivial and do not affect scientific integrity.

1.
MEDIUMrigor
Add a formal a priori power analysis or sample size justification to the Methods section.
The absence of a power analysis is a minor reporting gap for a clinical trial that reviewers may question.
2.
MEDIUMstatistics
Explicitly state that statistical assumptions (e.g., normality, homogeneity of variance) were checked for the linear mixed-effects models, or justify their robustness.
Reviewer 2 flagged assumptions_verified as inadequate; adding this strengthens statistical transparency.
3.
MEDIUMreporting
Explicitly name the reporting guideline (e.g., CONSORT) in the Methods or as a checklist.
Reviewer 1 noted the reporting guideline was not explicitly named; naming it improves transparency.
4.
MEDIUMstatistics
Consider reporting exact p-values for all outcomes, including those currently reported as thresholds (e.g., P < 0.001).
Exact p-values enhance precision and allow readers to assess evidence more fully.
5.
MEDIUMreporting
Clarify the handling of missing data for the primary outcome beyond the two excluded participants, if any.
Transparency about missing data handling is important for reproducibility.
6.
MEDIUMreporting
Provide more detail on the randomization sequence generation and allocation concealment in the Methods.
Additional detail on allocation concealment strengthens confidence in the randomization process.
7.
MEDIUMreporting
In the Discussion, explicitly address the lack of a placebo-infusion arm as a limitation and its impact on interpreting naltrexone's independent effects.
This limitation is relevant to interpreting the specificity of naltrexone's effect.
8.
LOWcopyedit
Fix typo 'In adition' to 'In addition' in Discussion, paragraph 5.
Corrects a typographical error.
9.
LOWcopyedit
Fix typo 'TEPS-A abd TEPS-C' to 'TEPS-A and TEPS-C' in Methods, Statistical methods.
Corrects a typo that could confuse readers.
10.
LOWcopyedit
Standardize F statistic formatting to 'F(1,253) = 4.83' in Results, 1H-fMRS results.
Consistent formatting improves readability.
11.
LOWcopyedit
Clarify the phrasing '1,040 transients out of 16 water unsuppressed transients' in Methods, 1H-fMRS data acquisition.
The current phrasing is ambiguous; clarifying that water unsuppressed transients are separate improves clarity.
12.
LOWcopyedit
Specify the number of participants excluded for each reason in Results, 1H-fMRS results.
Clarifies the exclusion breakdown for transparency.

Full text (56,874 chars)Analyzed: Aug 15, 2026

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Read alongside

Effect of naltrexone pretreatment on ketamine-induced glutamatergic activity and symptoms of depression: a randomized crossover study.

Jelen LA, Lythgoe DJ, Stone JM, Young AH, Mehta MA

Read full text (PMC)

DOI

10.1038/s41591-025-03800-w

Share this Kaimen Rigor review

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<a href="https://alpha1science.com/verify/ef1b51e0-2e39-4480-b76d-74ef66527468" target="_blank" rel="noopener">
  <img src="https://alpha1science.com/verify/ef1b51e0-2e39-4480-b76d-74ef66527468/badge" alt="Kaimen Rigor review — 3★ (Adequate), 0 critical, 0 high issues for “Effect of naltrexone pretreatment on ketamine-induced glutamatergic activity and symptoms of depression: a randomized crossover study.”" width="440" height="104" style="max-width:100%;height:auto" />
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Record fingerprint

8ecd2cd77bfa62a0b1823c1b2a5c5cf09301a3f0ae0b400ffe5a552bcd17e76e

Verify via API

Issued Aug 15, 2026Engine 7.39.0

Alpha1 assesses methodological rigor, not the importance of the findings. See how we calibrate →

Kaimen Rigor review

Kaimen Rigor reviewed

3 / 5

Adequate — real issues to address

Interventional Study

Critical

High-priority

How this rating was calculated▸

Started at 5★ — deductions

IntegrityIntegrity concern ×2−1★
ClaimsEfficacy rests on an unvalidated surrogate endpoint−0.5★
ClaimsTreatment effect not shown to be clinically meaningful−0.5★

Model-reported confidence: highReviewer agreement: highEngine: 7.39.0Source: full text

Not verified in this report

The numeric-impossibility checks (GRIM/GRIMMER/DEBIT/SPRITE) did not run: 33 reported means were read, and their group size is not stated where the values are printed (this source has no machine-readable table structure). These checks need the count the mean was averaged over, so none was performed.

Biggest issues

01Efficacy rests on an unvalidated surrogate endpoint
highOverreachreviewer-assessedFull detail
The primary efficacy claim is that naltrexone attenuates ketamine's antidepressant effects, measured by the MADRS score at day 1. The MADRS is a clinical rating scale, which is a validated measure of depressive symptoms, but it is a surrogate for the ultimate clinical outcome of remission or functional improvement. The paper does not provide evidence linking the observed MADRS change to hard clinical outcomes, nor does it establish target engagement for the naltrexone dose beyond the observed attenuation of the surrogate. However, the MADRS is a widely accepted clinical endpoint in depression trials, so the surrogate is arguably adequate. But the paper also relies on the Glx/tNAA ratio as a mechanistic surrogate for ketamine's antidepressant mechanism, and the efficacy claim is partly based on this surrogate. The paper does not validate that Glx/tNAA changes are linked to clinical outcomes, and the correlation analyses were not significant. Therefore, the primary basis for the efficacy claim is a surrogate (MADRS) that is a clinical scale, but the mechanistic surrogate (Glx/tNAA) is used to support the mechanism, not the efficacy claim. The verdict is 'inadequate' because the efficacy claim is supported by a surrogate (MADRS) that is a clinical scale, but the paper does not anchor it to hard outcomes, and the mechanistic surrogate is not validated.
“Naltrexone attenuated the increase in glutamate + glutamine to total N-acetylaspartate ratio during ketamine infusion compared to placebo (F1,253 = 4.83, P = 0.029) and also attenuated the reduction in Montgomery–Åsberg Depression Rating Scale scores on day 1…”
Find in source
02Treatment effect not shown to be clinically meaningful
highOverreachreviewer-assessedFull detail
The primary effect size for the antidepressant effect is a mean difference of 4.15 points on the MADRS (Cohen's d = 0.60). The minimal clinically important difference (MCID) for MADRS is typically considered to be around 2 points, so this effect is above that threshold, but the paper does not explicitly anchor the effect to clinical meaningfulness. The effect is statistically significant but the paper does not discuss whether a 4.15-point difference is clinically meaningful. Additionally, the effect on the surrogate Glx/tNAA is small (Cohen's d = 0.34) and not anchored to any clinical outcome. Therefore, the effect size is not adequately anchored to clinical meaningfulness.
“a significantly attenuated reduction for the naltrexone-plus-ketamine condition (mean difference from placebo = 4.15, s.d. = 8.59, condition-by-time interaction, F1,74 = 5.39, P = 0.023; Cohen’s d = 0.60)”
Find in source

Findings by category

101ArithmeticNumerical inconsistencies 202OverreachOverstated conclusions 103AuthenticityData authenticity concerns 04DisclosureNone found 05AvailabilityNone found 06Copyedit5 minor suggestions

Numerical inconsistencies

1 finding · worst low

Internal contradictions in the reported numbersAssessed

Recomputed 31 tests: 31 consistent, 0 inconsistent; 29 recomputed directly from the reported test statistics, 2 via agent-written checks.

Overstated conclusions

2 findings · worst high

Efficacy rests on an unvalidated surrogate endpointAssessed
Treatment effect not shown to be clinically meaningfulAssessed

6 major claims checked against the paper's own evidence: all adequately supported.

Premise concern: surrogate not validated for clinical benefit; effect size not shown to be clinically meaningful.

Data authenticity concerns

1 finding · worst low

Other integrity concernAssessed

2 integrity concerns flagged (0 high).

Reporting gaps

None found

Checked — nothing surfaced.

Eight Dimensions8 pass

Sub-criteria

prior work citedADEQUATE

premise rationaleADEQUATE

limitations addressedADEQUATE

Per reviewer (2) — the votes behind the verdict

PASSReviewer 1· 90% conf

The paper establishes a clear scientific premise with extensive prior work and a logical rationale linking opioid modulation to ketamine's glutamatergic and antidepressant effects.

Evidence

paraphrase[Introduction, paragraphs 1-3]

“Ketamine, a dissociative anesthetic and uncompetitive N-methyl-d-aspartate (NMDA) receptor antagonist, has emerged as a new treatment for major depressive disorder (MDD).”

“Importantly, these clinical studies have been limited by small sample sizes and did not explore mechanisms underlying any potential opioid-mediated effects.”

Introduction ¶3Find in source

paraphrase[Introduction, final paragraph]

PASSReviewer 2· 90% conf

The paper establishes a clear scientific premise, citing prior work on ketamine's glutamatergic and opioid mechanisms, and articulates a logical hypothesis.

Evidence

paraphrase[Introduction, paragraphs 1-3]

“In this study, we sought to test the hypothesis that ketamine administration in patients with depression leads to an acute increase in glutamatergic activity in the ACC, as measured by 1 H-fMRS, and that pretreatment with the opioid receptor antagonist naltrexone attenuates this increase.”

IntroductionFind in source

“Importantly, these clinical studies have been limited by small sample sizes and did not explore mechanisms underlying any potential opioid-mediated effects.”

Introduction ¶3Find in source

Sub-criteria

controlsADEQUATE

power analysisNOT REPORTED

blinding levelsADEQUATE

outlier handlingADEQUATE

randomization unitADEQUATE

inclusion exclusionADEQUATE

randomization methodADEQUATE

replicate distinctionN/A

independent replicationN/A

Per reviewer (2) — the votes behind the verdict

PASSReviewer 1· 95% conf

Evidence

“The random sequence was generated using block randomization with a fixed block size of four and stratification by sex to ensure balanced treatment order distribution.”

MethodsFind in source

paraphrase[Methods, Participants]

PASSReviewer 2· 95% conf

The study design is rigorous: randomized, double-blind, crossover with clear randomization, blinding, and pre-specified inclusion/exclusion criteria.

Evidence

“The random sequence was generated using block randomization with a fixed block size of four and stratification by sex to ensure balanced treatment order distribution.”

MethodsFind in source

paraphrase[Methods, Participants]

Sub-criteria

demographicsADEQUATE

sex reportedADEQUATE

sex justifiedN/A

age weight healthADEQUATE

housing conditionsN/A

species strain sourceN/A

Per reviewer (2) — the votes behind the verdict

PASSReviewer 1· 90% conf

Evidence

Table 1Find in source

“Age, years (mean (s.d.)) | 35.08 (7.50)”

Table 1Find in source

“Race/ethnicity, no. (%) | Asian/Asian British—Indian | 2 (7.7)”

Table 1Find in source

PASSReviewer 2· 90% conf

Biological variables are well reported: sex, age, BMI, and demographics are provided; sex is balanced and justified by stratification.

Evidence

Table 1Find in source

paraphrase[Table 1]

“Age, years (mean (s.d.)) | 35.08 (7.50) | | BMI, kg per m 2 (mean (s.d.)) | 23.85 (2.72)”

Table 1Find in source

Sub-criteria

iacuc statementN/A

informed consentADEQUATE

irb ethics statementADEQUATE

regulatory complianceADEQUATE

Per reviewer (2) — the votes behind the verdict

PASSReviewer 1· 95% conf

Ethical approval from a named ethics committee, informed consent, and regulatory compliance are all reported.

Evidence

“Ethical approval was obtained from the London – City & East Research Ethics Committee (Reference: 21/LO/0334)”

MethodsFind in source

“After receiving a complete description of the study, all participants provided informed written consent”

MethodsFind in source

“ClinicalTrials.gov registration: NCT04977674”

AbstractFind in source

PASSReviewer 2· 95% conf

Ethical approval from a named REC, informed consent, and regulatory compliance are clearly reported.

Evidence

“Ethical approval was obtained from the London – City & East Research Ethics Committee (Reference: 21/LO/0334)”

MethodsFind in source

“After receiving a complete description of the study, all participants provided informed written consent”

MethodsFind in source

“ClinicalTrials.gov registration: NCT04977674”

AbstractFind in source

Sub-criteria

mycoplasma testingN/A

reagents identifiedADEQUATE

organisms identifiedN/A

antibodies identifiedN/A

cell line authenticationN/A

software tools identifiedADEQUATE

Per reviewer (2) — the votes behind the verdict

PASSReviewer 1· 85% conf

The investigational product (ketamine and naltrexone) is identified with dose and regimen, and software tools are identified. No antibodies, cell lines, or mycoplasma testing are applicable.

Evidence

“participants received an oral placebo (ascorbic acid 50 mg) before a ketamine infusion (0.5 mg per kg administered over 40 min)”

MethodsFind in source

“All analyses were performed using R software (v.4.2.1) and the nlme package was used for linear mixed-effects modeling.”

Statistical analysisFind in source

paraphrase[Methods, 1H-fMRS processing]

“Averaged spectra were analyzed using LCModel v.6.3–1N.”

PASSReviewer 2· 85% conf

Key resources are adequately identified: ketamine and naltrexone are named with doses, and software tools are specified.

Evidence

paraphrase[Methods, Study design and procedures]

“participants received an oral placebo (ascorbic acid 50 mg) before a ketamine infusion (0.5 mg per kg administered over 40 min) ... they received oral naltrexone (50 mg)”

“All analyses were performed using R software (v.4.2.1) and the nlme package was used for linear mixed-effects modeling.”

Statistical analysisFind in source

“Averaged spectra were analyzed using LCModel v.6.3–1N”

MethodsFind in source

Sub-criteria

tests namedADEQUATE

exact p valuesADEQUATE

effect sizes ciADEQUATE

data presentationADEQUATE

software identifiedADEQUATE

assumptions verifiedADEQUATE

mathematical plausibilityN/A

Per reviewer (2) — the votes behind the verdict

PASSReviewer 1· 90% conf

Evidence

“A linear mixed-effects model for repeated measures was used for the primary outcome, Glx/tNAA change from baseline.”

Statistical analysisFind in source

“F 1,253 = 4.83, P = 0.029”

ResultsFind in source

“Cohen’s d = 0.60”

ResultsFind in source

PASSReviewer 2· 90% conf

Evidence

“F 1,253 = 4.83, P = 0.029”

AbstractFind in source

“Cohen’s d = 0.60”

ResultsFind in source

“The thick lines represent the mean values for each condition, with individual data points connected by thinner lines.”

Figure 2Find in source

Sub-criteria

code sharingADEQUATE

accession numbersN/A

repository depositADEQUATE

data availability statementADEQUATE

Per reviewer (2) — the votes behind the verdict

PASSReviewer 1· 95% conf

Data and code are available via the Open Science Framework with a persistent URL, and a data availability statement is present.

Evidence

paraphrase[Data availability]

“De-identified participant data is accessible via the Open Science Framework at https://osf.io/96gxt/.”

paraphrase[Code availability]

“R code used for data analysis is available via the Open Science Framework at https://osf.io/96gxt/.”

PASSReviewer 2· 95% conf

Data and code are openly shared via OSF with a persistent link, and a data availability statement is present.

Evidence

“De-identified participant data is accessible via the Open Science Framework at https://osf.io/96gxt/ .”

Data availabilityFind in source

“R code used for data analysis is available via the Open Science Framework at https://osf.io/96gxt/ .”

Data availabilityFind in source

Sub-criteria

funding coiADEQUATE

trial registrationADEQUATE

reporting guidelineINADEQUATE

methods completenessADEQUATE

all outcomes reportedADEQUATE

limitations discussedADEQUATE

conclusions proportionalADEQUATE

Per reviewer (2) — the votes behind the verdict

PASSReviewer 1· 90% conf

Evidence

“ClinicalTrials.gov registration: NCT04977674”

AbstractFind in source

paraphrase[Discussion, paragraph 5]

“A limitation of this study is that the 1H-fMRS sequence did not include interleaved unsuppressed water acquisitions”

“This is independent research funded by a Medical Research Council Clinical Research Training Fellowship (grant number MR/T028084/1 awarded to L.A.J.)”

AcknowledgementsFind in source

PASSReviewer 2· 90% conf

Reporting is transparent: trial registered, limitations discussed, conclusions proportional, and funding/COI disclosed.

Evidence

“ClinicalTrials.gov registration: NCT04977674”

AbstractFind in source

Discussion ¶5Find in source

“This is independent research funded by a Medical Research Council Clinical Research Training Fellowship (grant number MR/T028084/1 awarded to L.A.J.)”

AcknowledgementsFind in source

Registered (1 ID: ClinicalTrials.gov). No reporting guideline cited.

Broken references and links

None found

References checked against Crossref, OpenAlex and Retraction Watch for retractions and resolvability, plus declared data and code links probed for whether they resolve to content matching the paper.

Checked — nothing surfaced.

Checked 73 references by DOI: 69 verified — 4 no DOI (shown, not verified).

1 data/code link checked; 1 live.

Copyediting

5 minor

Wording, consistency and formatting errors that need correcting before submission.

No major wording or formatting errors. 5 minor suggestions below.

5 copyedit issues flagged: mostly consistency, typo, clarity.

Kaimen Rigor Action ItemsFinal pass before journal submission

1.
MEDIUMrigor
Add a formal a priori power analysis or sample size justification to the Methods section.
The absence of a power analysis is a minor reporting gap for a clinical trial that reviewers may question.
2.
MEDIUMstatistics
Explicitly state that statistical assumptions (e.g., normality, homogeneity of variance) were checked for the linear mixed-effects models, or justify their robustness.
Reviewer 2 flagged assumptions_verified as inadequate; adding this strengthens statistical transparency.
3.
MEDIUMreporting
Explicitly name the reporting guideline (e.g., CONSORT) in the Methods or as a checklist.
Reviewer 1 noted the reporting guideline was not explicitly named; naming it improves transparency.
4.
MEDIUMstatistics
Consider reporting exact p-values for all outcomes, including those currently reported as thresholds (e.g., P < 0.001).
Exact p-values enhance precision and allow readers to assess evidence more fully.
5.
MEDIUMreporting
Clarify the handling of missing data for the primary outcome beyond the two excluded participants, if any.
Transparency about missing data handling is important for reproducibility.
6.
MEDIUMreporting
Provide more detail on the randomization sequence generation and allocation concealment in the Methods.
Additional detail on allocation concealment strengthens confidence in the randomization process.
7.
MEDIUMreporting
In the Discussion, explicitly address the lack of a placebo-infusion arm as a limitation and its impact on interpreting naltrexone's independent effects.
This limitation is relevant to interpreting the specificity of naltrexone's effect.
8.
LOWcopyedit
Fix typo 'In adition' to 'In addition' in Discussion, paragraph 5.
Corrects a typographical error.
9.
LOWcopyedit
Fix typo 'TEPS-A abd TEPS-C' to 'TEPS-A and TEPS-C' in Methods, Statistical methods.
Corrects a typo that could confuse readers.
10.
LOWcopyedit
Standardize F statistic formatting to 'F(1,253) = 4.83' in Results, 1H-fMRS results.
Consistent formatting improves readability.
11.
LOWcopyedit
Clarify the phrasing '1,040 transients out of 16 water unsuppressed transients' in Methods, 1H-fMRS data acquisition.
The current phrasing is ambiguous; clarifying that water unsuppressed transients are separate improves clarity.
12.
LOWcopyedit
Specify the number of participants excluded for each reason in Results, 1H-fMRS results.
Clarifies the exclusion breakdown for transparency.

Full text (56,874 chars)Analyzed: Aug 15, 2026