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
Alain F. Kalmar, Pascal Sienaert, Filip Bouckaert, Steffen Rex
BJPsych Open July 1, 2026 DOI: 10.1192/bjo.2026.12040 (opens in new tab) via OpenAlex
Summary
AI-generated from the abstractNitrous 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.
Study at a glance
| Characteristics | Review Randomized Placebo-controlled Pilot study Peer reviewed |
|---|---|
| Duration | 1 h treatment, per patient-year |
| Keywords | Nitrous oxide Greenhouse gas Mood Externality Inhalation |
| Key finding | A single one-hour nitrous oxide treatment for depression generates about 150 kg CO2-equivalents, rising to about 7.8 t per patient-year, and these environmental externalities should be incorporated into evaluation. |
Abstract
Summary Nitrous oxide is being investigated as a treatment for therapy-resistant depression, yet its environmental implications as a potent greenhouse gas are largely unaddressed. A single 1 h treatment generates ∼150 kg CO 2 -equivalents, rising to ∼7.8 t per patient-year, highlighting the need to incorporate environmental externalities into evaluation.