The popular party drug, ketamine, could be used to help some people suffering from severe depression, according to a new study conducted by researchers from the Oxford Health NHS Foundation Trust and the University of Oxford.

Published in the Journal of Psychopharmacology, the study describes using ketamine intravenous infusions in people as a treatment for severe depression. Researchers reported that ketamine had a rapid beneficial effect in some patients with serious depression who were not responding to other treatments.

"Intravenous ketamine is an inexpensive drug which has a dramatic, but often short-term, effect in some patients whose lives are blighted by chronic severe depression," Rupert McShane, a consultant psychiatrist and researcher at Oxford University who led the study, said in a press release.

In the study, 28 participants diagnosed with severe and treatment-resistant depression were subjected to ketamine treatment for three weeks. Patients either received three or six ketamine infusions - 80 milligrams dose - each lasting 40 minutes. They reported their mood symptoms daily by either text or email.

Memory tests were carried out a few days after the final infusion, as memory loss is a common side effect of depression treatments. The results showed that three days after the last infusion, the depression scores had cut in half for 29 percent of the patients.

In those that responded to the treatment, a third of them felt a benefit which lasted at least three weeks and 15 percent took more than two months to relapse.

"We've seen remarkable changes in people who've had severe depression for many years," McShane said. "It's very moving to witness. Patients often comment that that the flow of their thinking seems suddenly freer. For some, even a brief experience of response helps them to realize that they can get better and this gives hope".

Ketamine, a horse tranquillizer, has become a popular recreational drug for partygoers. Ketamine is also a licensed medical drug, used as an anesthetic and to relieve pain

None of the patients suffered from impaired brain function or bladder side effects, which often occurs when used as a recreational drug. Some people did experience other side effects such as anxiety during the infusion or being sick, with one fainting. Many patients had episodes of suicidal behavior during the study.

"We now need to build up clinical experience with ketamine in a small number of carefully monitored patients," McShane concluded. "By trying different infusion regimes and adding other licensed drugs, we hope to find simple ways to prolong its dramatic effect."

A total of 400 infusions have now been given to 45 patients.