Ketamine, a drug used as an anesthetic and pain reliever in hospitals and also taken illegally as a recreational hallucinogenic, has been shown to help reduce symptoms of depression faster than some existing antidepressants.

According to the World Health Organization, depression affects an estimated 350 million people globally, making it one of the most common illnesses worldwide. For patients who take antidepressants, the benefits often take two to three weeks to kick in after the first dose, and the optimal effect is not reached for six to 10. This can be a critical issue for patients whose depression is so severe that such a delay could be life-threatening.

Small clinical trials have shown that ketamine can relieve depression in a matter of hours, even in patients with treatment-resistant depression and major depressive disorder with suicidal thoughts. However, the studies involved small numbers of patients and larger trials are needed to determine the extent of potential benefits. Some physicians also worry about the long-term effects of ketamine use and point out that its antidepressant effects wear off quickly.

A recent study published in Scientific Reports analyzed 8 million reports from the federal government and found patients who received low doses of ketamine and other therapeutics had lower reports of depression than patients who took any other combination of medicine for pain.

The drug’s success has pharmaceutical companies excited about the possibility of creating a whole new class of drugs for depression. One chemical variant of ketamine is in the final phase of testing before being considered by the Food and Drug Administration.