Sustained mood improvement with laughing gas exposure (SMILE): a randomised, placebo-controlled pilot trial of nitrous oxide for treatment-resistant depression: commentary, Kalmar et al
BJPsych Open July 1, 2026 Alain F. Kalmar, Pascal Sienaert, Filip Bouckaert et al.
Nitrous oxide, a potent greenhouse gas, is being explored as a treatment for therapy-resistant depression, but its environmental costs are often ignored. A single one-hour treatment produces about 150 kilograms of CO2-equivalents, and a year of treatment for one patient generates roughly 7.8 metric tons of CO2-equivalents. The authors argue that these environmental externalities should be factored into assessments of the therapy's overall value.