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Glutamate plus glutamine to GABA ratio as a predictor of ketamine response in treatment-resistant depression: A double-blind, randomized, open-label extension study.

Yohei Ohtani, Hideaki Tani, Shiori Honda, Kie Nomoto-Takahashi, Taisuke Yatomi, Kengo Yonezawa, Sota Tomiyama, Nobuhiro Nagai, Keisuke Kusudo, Sotaro Moriyama, Yoshihiro Noda, Shinsuke Koike, Richard A.E. Edden, Hiroyuki Uchida, Shinichiro Nakajima

Journal of Affective Disorders August 15, 2025 DOI: 10.1016/j.jad.2025.04.165 (opens in new tab)

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Study at a glance

AI-extracted from the abstract
Characteristics Double-blind randomized clinical trial with an open-label extension Peer reviewed
Sample size 30
Population Patients with treatment-resistant depression
Intervention Ketamine
Topics Depression Ketamine Esketamine
Keywords 1h-mrs Excitatory/inhibitory balance Gaba Glx Predictor Ketamine therapy Brain chemistry Neurotransmitter balance Psychiatric biomarkers
Citations 3
Key findings A higher baseline Glx/GABA ratio in the dorsal anterior cingulate cortex predicted greater improvement in depressive symptoms after ketamine treatment.

Abstract

Approximately 30 % of patients with treatment-resistant depression (TRD) respond to ketamine; however, no replicable predictors of response have been reported. The imbalance between excitatory and inhibitory neurotransmissions may be implicated in the mechanism of action of ketamine. This study aimed to evaluate whether the ratio of glutamate and glutamine (Glx) to GABA levels at baseline in the dorsal anterior cingulate cortex (dACC) could predict ketamine response in patients with TRD. This exploratory study analyzed data from a double-blind randomized clinical trial with an open-label extension study (jRCTs031210124). Fifteen participants in the ketamine group and 15 of 16 participants in the placebo group received repeated intravenous ketamine during the double-blind and open-label extension periods, respectively. We measured Glx and GABA levels in the dACC before and after treatment during the double-blind period using proton magnetic resonance spectroscopy. The 17-item Hamilton Depression Rating Scale (HDRS-17) was measured for depressive symptomatology. General linear models were used to examine the relationship between baseline Glx/GABA ratio and HDRS-17 score changes. Changes in HDRS-17 scores (mean (±SD)) following ketamine treatment were -4.9 (6.5) and -4.9 (5.2) in the double-blind and open-label periods, respectively. A higher baseline dACC Glx/GABA ratio was correlated with greater improvement in HDRS-17 (β = -0.42, p = 0.040). In the ketamine group, a reduction in the dACC Glx/GABA ratio was correlated with greater HDRS-17 improvement (β = 0.74, p = 0.009) with no such association in the placebo group. These results suggest that excitatory-inhibitory imbalance in the dACC may predict the efficacy of ketamine in TRD.

Comparable studies

Other randomized controlled trials on ketamine for depression, most cited first.

Study Year Design Participants
Antidepressant Efficacy of Ketamine in Treatment-Resistant Major Depression: A Two-Site Randomized Controlled Trial Patients with treatment-resistant major depression experiencing a major depressive episode 2013 Randomized controlled trial n = 73
Efficacy and Safety of Flexibly Dosed Esketamine Nasal Spray Combined With a Newly Initiated Oral Antidepressant in Treatment-Resistant Depression: A Randomized Double-Blind Active-Controlled Study Adults with moderate to severe nonpsychotic depression and a history of nonresponse to... 2019 Phase 3, double-blind, active-controlled, multicenter randomized controlled trial n = 227
Efficacy of Esketamine Nasal Spray Plus Oral Antidepressant Treatment for Relapse Prevention in Patients With Treatment-Resistant Depression Adults with treatment-resistant depression who achieved stable remission or stable... 2019 Phase 3, multicenter, double-blind, randomized withdrawal study n = 297
Efficacy and Safety of Intranasal Esketamine Adjunctive to Oral Antidepressant Therapy in Treatment-Resistant Depression Adults with DSM-IV-TR diagnosis of major depressive disorder and history of inadequate... 2017 Phase 2, double-blind, doubly randomized, delayed-start, placebo-controlled study n = 67
Efficacy and Safety of Intranasal Esketamine for the Rapid Reduction of Symptoms of Depression and Suicidality in Patients at Imminent Risk for Suicide: Results of a Double-Blind, Randomized, Placebo-Controlled Study Depressed patients at imminent risk for suicide 2018 Randomized controlled trial n = 68

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