Ketamine, a drug currently used as an anesthetic, was found to have a rapid antidepressant effect on patients with treatment resistant major depression according to researchers presenting their work at the American Psychiatric Association's 2013 annual meeting. Research conducted by James Murrough, M.D., an Assistant Professor at the Icahn School of Medicine at Mount Sinai in New York, showed that ketamine's antidepressant effects were significant and could be observed within 24 hours, versus the days or weeks other antidepressants can take to be effective.

The study is the largest clinical trial to date on the effects of ketamine on mood disorders. The goal of the research was to discover if a single infusion of ketamine would prove superior to an "active" placebo. The study tracked 73 patients with treatment resistant major depression and provided half with a single intravenous infusion of ketamine and the other half with midazolam.  Midazolam has similar anesthetic effects as ketamine, but without the antidepressant qualities. Patients were interviewed after 24 hours and again at two, three and seven days.

At 24 hours post-infusion, the response rate in the ketamine arm was 63.8%, compared to 28.0% in the midazolam arm (P =0.006). At Day 7, the response rate in the ketamine arm was 45.7%, compared to 18.2% in the midazolam arm (P < 0.034). The study found that all the patients given ketamine showed sustained improvement up to the seventh day when evaluated on the Montgomery-Asberg Depression Scale (MADRS).

This work was presented at the 166th Annual Meeting of the American Psychiatric Association in San Francisco, California, USA.