A new systematic review and meta-analysis published in The Lancet examined seven clinical trials involving 247 participants and found that nitrous oxide may produce rapid reductions in depressive symptoms, though these effects appear to be short-lived. When administered at 50% concentration via inhalation, nitrous oxide showed significant symptom reductions compared to placebo at 2 and 24 hours, but improvements were not sustained at one week. Repeated dosing showed more durable results, and higher concentrations (50% vs. 25%) appeared more effective but caused more side effects. Adverse events were generally mild, including nausea, dizziness, and headache. However, the authors noted that most trials were small and early-phase, with substantial gaps remaining in the research—particularly regarding long-term efficacy, maintenance strategies, and use in adolescents or those with bipolar depression. They concluded that while nitrous oxide shows promise as a rapid-acting antidepressant, larger trials are needed to determine its clinical utility.