Journal of affective disorders
January 23, 2026
Reinhard Janssen-Aguilar, Jithin Joseph, Huda Al-Shamali et al.
In a retrospective chart review of 209 adults with treatment-resistant depression treated with intravenous ketamine, depressive and anxiety symptoms improved significantly over four or six infusions, but the improvements were modest and highly variable across individuals. Anxiety symptoms improved more slowly and less robustly than depressive symptoms. End-of-treatment response and remission rates were numerically higher after six infusions than after four, but the difference was not statistically significant. Four distinct patterns of symptom change emerged for both depression and anxiety, highlighting the heterogeneity of treatment response. Durability after six infusions could not be assessed because follow-up data were available only for the four-infusion group.
BJPsych open
September 12, 2025
Karim S Ladha, Jiwon Lee, Gabriella F Mattina et al.
A pilot trial tested the feasibility of a four-week course of nitrous oxide compared with midazolam (an active placebo) for treatment-resistant depression. Forty participants were randomly assigned to weekly one-hour inhalations of either 50% nitrous oxide or 50% oxygen plus intravenous midazolam. Recruitment, withdrawal, adherence, and missing data rates met feasibility criteria. Depression severity, measured by the MADRS scale, changed by -20.5% in the nitrous oxide group and -9.0% in the placebo group. Adverse events were mostly mild to moderate and transient. The results support conducting a full-scale trial.
PloS one
January 1, 2024
Karim S Ladha, Jiwon Lee, Gabriella F Mattina et al.
A pilot trial will test whether weekly inhaled nitrous oxide is feasible and preliminarily effective for treatment-resistant depression compared with the active placebo midazolam. Forty participants will receive either nitrous oxide (1 hour at 50% concentration) plus intravenous saline or oxygen (1 hour at 50% concentration) plus intravenous midazolam once per week for 4 weeks, with 6 weeks of follow-up. Feasibility will be assessed by recruitment and withdrawal rates, adherence, missing data, and adverse events. The main exploratory clinical outcome is change in depression scores at day 42. Results will guide a future definitive trial.