In a new study at Washington University School of Medicine in St. Louis, researchers gave laughing gas to 20 patients who had treatment-resistant clinical depression. They found two-thirds experienced an improvement in symptoms within 24 hours of receiving nitrous oxide. By contrast, one-third of the same patients reported improved symptoms after treatment with a placebo.
 

The findings, presented this week at a meeting of the American College of Neuropsychopharmacology in Scottsdale, Ariz., were published online in the journal Biological Psychiatry.
 

“Our findings need to be replicated, but we think this is a good starting point, and we believe therapy with nitrous oxide eventually could help many people with depression,” said lead investigator Peter Nagele, M.D., an assistant professor of anesthesiology.
 

As many as one-third of patients with clinical depression do not respond to existing treatments. Laughing gas has few side effects — the most common are nausea and vomiting — and it leaves the body very quickly after people stop breathing the gas.
 

That’s why the researchers believe the improvement in symptoms a day later is real and not a side effect of the nitrous oxide.