Laughing gas, AKA nitrous oxide or NOS, has been shown to be effective in treating depression, according to a new study.

Nitrous oxide is a common recreational drug that gives users a short mood boost – hence the nickname ‘laughing gas’. Officially-speaking, it’s one of the most common anaesthetics, used by hospitals, dental surgeries, and paramedics.

While it was initially thought that laughing gas’ mood-lifting properties wear off quickly, researchers at Washington University School of Medicine in St Louis, Missouri, have discovered that one small dose of the substance can improve symptoms of depression for up to two weeks.

The study looked at 24 people with treatment-resistant depression and gave them a half-dose nitrous oxide, a full dose, or a placebo mixture of air and oxygen. They were given one treatment a month for three months.

After two weeks, depression symptoms for those with the half-dose treatment had reduced by an average of five points on a commonly used depression rating scale, compared with those who had the placebo.

Those on the full-dose treatment found that depression symptoms reduced a little more, though the difference was so small that it could have arisen by chance. The half-dose group also had a much lower incidence of side effects, such as nausea, headaches, and light-headedness.

Similar to ketamine, nitrous oxide has the benefit of improving mood quickly, says Peter Nagele, who headed the study. “Something happens in the brain – it’s like flipping a switch. But how this works, no one knows,” he told New Scientist.

Scientists are increasingly looking to psychedelics for new ways to treat depression. Earlier this year, the first ketamine clinic opened in the UK, which combines psychotherapy with ketamine treatment, making these therapies more widely accessible to the public. 

Researchers recently found that psilocybin, the active compound in magic mushrooms, has been proven to be as effective as antidepressants in treating depression. Previous studies have also shown that one dose of magic mushrooms can reduce symptoms of depression for as long as five years.