Association between Intravenous Ketamine Treatment and Cognitive Function in Patients with Treatment-Resistant Depression: A Double-Blind, Randomized, Placebo-Controlled Trial
Pharmacopsychiatry July 7, 2026 Kie Nomoto, Yohei Ohtani, Taisuke Yatomi et al.
In a double-blind, randomized, placebo-controlled trial, 34 Japanese patients with treatment-resistant depression received four intravenous doses of either ketamine (0.5 mg/kg) or saline. No significant differences emerged between the groups on objective or subjective cognitive function measures. Among ketamine-treated patients, those who responded to treatment (at least 50% reduction on the Montgomery-Åsberg Depression Rating Scale) showed greater improvement in subjective cognitive function than non-responders. Participants with weaker inhibitory control at baseline experienced larger reductions in depressive symptoms after ketamine. Repeated ketamine administration did not worsen cognitive function compared to placebo, suggesting cognitive safety, and baseline cognitive control deficits may predict better treatment response.