Sept. 23, 2014 -- Every year, 13 million to 14 million Americans have major depression. Of those who seek treatment, 30% to 40% will not get better or fully recover with standard antidepressants.

That puts them at greater risk of alcohol and drug abuse, hospitalization, and suicide attempts. Now, though, a growing body of research shows there may be new hope: the anesthetic drug ketamine.

Ketamine has a reputation as an illicit party drug due to its hallucinogenic effects. But in a handful of ketamine clinics around the country, people who weren't helped by standard treatments are getting a series of infusions to ease their depression. The drug has also been used in emergency rooms for curbing suicidal thoughts, making it a potential lifesaver.

“The benefits I’ve seen are pretty impressive, and the data are very strong,” says psychiatrist Kyle Lapidus, MD, PhD. He's an assistant professor of psychiatry and neuroscience at Stony Brook University. Lapidus says there have been a large number of positive studies, though the number of participants in those studies has been small.

Ketamine acts quickly -- often within hours or less -- and health care professionals who give it to patients at therapeutic doses say it has mild and brief side effects in most people. But it hasn't been thoroughly studied for long-term safety and effectiveness, and the FDA hasn't approved it to treat depression. “The pace of research can be slow for people who are suffering,” Lapidus says.

He says it’s not uncommon for doctors to go "off-label" (using a drug for a purpose other than its approved one) when treating patients. And in the case of ketamine, the research, including his own, has convinced him that it can help depressed patients. Lapidus runs a Manhattan clinic called US Ketamine. Soon, he will open a second clinic on Long Island.