Washington University researchers in St. Louis are studying the use of nitrous oxide, also known as laughing gas, as a treatment for those having suicidal thoughts. The gas is commonly used in dental offices to reduce pain and anxiety.

About 85% of those who attempt suicide are clinically depressed. As many as one-third of patients with clinical depression don’t respond to existing drug and psychotherapy treatments.

Most standard antidepressant drugs affect norepinephrine and serotonin receptors in the brain, but they can take weeks to improve a person’s symptoms. Nitrous oxide interacts with a different type of receptor in the brain — NMDA glutamate receptors — and improves symptoms in some patients within hours, according to Dr. Peter Nagele, an associate professor of anesthesiology and of genetics.

“Nitrous oxide may very quickly improve depression in these patients,” says Nagele. “The gas has very few side effects because it leaves the body very quickly once people stop breathing it. However, it appears from our previous research that the antidepressant effects of nitrous oxide may linger in the brain long after the drug is out of the body.”

In a new study — funded by a grant from the American Foundation for Suicide Prevention — people who have attempted suicide will breathe a mixture of oxygen and nitrous oxide for one hour, every other day, for one week.

Half of the anticipated 50 study patients will receive the combination of nitrous oxide and oxygen, along with antidepressant drugs or talk therapy normally prescribed during such a hospitalization. The rest of the patients in the study will receive standard treatment with antidepressants and psychotherapy, and will receive oxygen without any nitrous oxide for one hour, every other day, for a week.

Suicide is one of the top 10 causes of death in the U.S. and is the 10th leading cause of death in Missouri. Among Missourians ages 10-24, suicide is the second leading cause of death. On average, one person in the state dies by suicide every eight hours.