Laughing gas might ease symptoms of depression, study finds

The dentist's office might be the last place you'd look to find a quick cure for an implacable bout of depression.

New research, however, suggests that laughing gas - the mixture of nitrous oxide and oxygen that eases the pain and anxiety of having dental work - may help ease treatment-resistant depression in about the time it takes to fill a cavity.

Interest in laughing gas as an antidepressant began with another sedative-turned-party-drug - ketamine.

The anesthetic ketamine induces a euphoric "out-of-body" high. When administered to the suicidally depressed, it is thought to be a promising "rescue" drug that offers quick relief, filling the four-to-six-week gap needed for many standard antidepressant medications to take full effect.

Like ketamine, nitrous oxide is an antagonist of the brain's NMDA receptor, a key bit of the cerebral machinery. Psychiatrists and anesthesiologists at Washington University in St. Louis, Missouri in the United States wondered whether nitrous oxide - a far less addictive drug than ketamine and one that may have fewer unforeseen side effects - might have the same benefits.

In a small pilot study published in the journal Biological Psychiatry, researchers compared the effects of an hour of inhaled nitrous oxide on 20 patients whose depression had failed to yield to the standard antidepressants.