Psychiatry and clinical neurosciences
December 1, 2024
Yohei Ohtani, Hideaki Tani, Kie Nomoto-Takahashi et al.
13 citations
In a double-blind randomized placebo-controlled trial with 34 Japanese patients suffering from treatment-resistant depression, intravenous ketamine (0.5 mg/kg) given twice a week for two weeks did not show a statistically significant advantage over placebo in reducing depression scores when all participants were analyzed together. However, among those who completed the full treatment protocol, ketamine led to a significantly greater reduction in depressive symptoms than placebo. Higher baseline depression severity and body mass index were linked to greater symptom improvement with ketamine. Adverse events were more common with ketamine but no serious events occurred. These results suggest ketamine may be effective for treatment-resistant depression across diverse ethnic groups.
Journal of affective disorders
August 15, 2025
Yohei Ohtani, Hideaki Tani, Shiori Honda et al.
3 citations
About 30% of people with treatment-resistant depression respond to ketamine, but reliable predictors of response have been lacking. This study examined whether the ratio of glutamate+glutamine (Glx) to GABA in the dorsal anterior cingulate cortex (dACC) could predict ketamine's effectiveness. In a double-blind randomized trial with an open-label extension involving 30 participants, a higher baseline Glx/GABA ratio in the dACC correlated with greater improvement in depression scores (measured by the HDRS-17). After ketamine treatment, a reduction in this ratio also correlated with symptom improvement. The findings suggest that an excitatory-inhibitory imbalance in the dACC may help predict which patients will benefit from ketamine therapy.
Psychiatry and Clinical Neurosciences
February 26, 2026
Kengo Yonezawa, M. Hirata, Hiroaki Takano et al.
1 citation
Psilocybin, a classic psychedelic compound, is being reexamined as a treatment for psychiatric disorders after decades of legal restrictions. Clinical trials report therapeutic effects for major depressive disorder, depressive symptoms in life-threatening illnesses, and some substance use disorders, with phase III trials for depression underway. Short-term side effects are generally mild and transient, but long-term effects need investigation. Neuroimaging research, mainly using MRI and EEG, is limited and focused on MDD, though ongoing trials include broader studies. Regulatory frameworks vary; controlled use is permitted in Switzerland, parts of the US, Canada, and Australia. Challenges remain, including the need for larger blinded trials and standardized protocols.
Psychiatry research. Neuroimaging
August 1, 2026
Kengo Yonezawa, Shinichiro Nakajima, Shuhei Shibukawa et al.
In patients with treatment-resistant depression, higher baseline levels of magnetic substances in the right nucleus accumbens and the left amygdala, measured by brain imaging, predicted a greater reduction in specific depressive symptoms after repeated ketamine infusions. The study included 17 Japanese patients and used a double-blind, randomized placebo-controlled design followed by an open-label phase. Baseline magnetic susceptibility in the right nucleus accumbens correlated with improvement in retardation symptoms, while baseline R2* in the left amygdala correlated with improvement in vegetative symptoms. These brain markers may help predict which patients will benefit from ketamine treatment.
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.