British researchers have made the surprising discovery that Ketamine, which has a reputation as an illicit recreational drug, is a potent antidepressant.

The findings, by scientists with the University of Hertfordshire, could open the door to using Ketamine — in medical use for 50 years as an anesthetic — as a mainline treatment for major and bipolar depression, Medical Xpress reports.

The conclusions are based on a new analysis of 21 published studies of the drug to treat people with depression. The results indicated depression was significantly reduced within four hours by a single administration of the drug — which could make it especially useful in treating people who are suicidal.

"The prospect of using Ketamine as an anti-depressant is a fascinating one, particularly in terms of its potential for rapidly alleviating depressive symptoms in individuals who haven't responded to more traditional treatments,” said Keith Laws, M.D., a professor of neuropsychology in the School of Life and Medical Sciences at the University of Hertfordshire.

“While conventional antidepressants and psychotherapy may take weeks or months to produce any effect, ketamine infusions produce benefits within hours."