The club drug, ketamine, also known as Special K, has shown itself to be helpful in the treatment of depression. But it has been slow to gain acceptance as an antidepressant because the relief it offers is often short-lived. While ketamine does act quickly and can reach people whose depression has not responded to other treatments, the relief it offers tends to fade quickly.

Most antidepressants take weeks to become fully effective, so a treatment that works in four hours provides unique benefits.

Researchers may have found a suitable niche for ketamine's unusual mode of action — suicide prevention. Ketamine is known to improve mood quickly — which is why it is so popular in clubs. But the quick boost it gives mood means it can also lift the spirits of those contemplating suicide and potentially save their lives.

In the study, researchers focused on the immediate effect, four hours later, of the drug. Half of a group of 68 people viewed as imminent suicide risks were given a nasal spray of esketamine, the biologically active form of the drug ketamine, twice weekly for four weeks. The other half of the participants in the double-blind study received a placebo, an inactive compound. All the people in the study were enrolled in comprehensive care for depression, which included other antidepressant medication.

People in the study who received ketamine showed significant improvements in both their symptoms of depression and in suicidal thoughts four hours after receiving esketamine.

Since most antidepressants can take weeks before becoming fully effective, a treatment that works in four hours provides unique benefits. This is particularly true for people who are suicide risks because of the way suicide attempts are often made.

Some suicides involve careful planning, but in some cases there are less than five minutes between the time a person decides to commit suicide and when they actually make the attempt. So a drug that can lift a person's mood quickly could offer the clinicians a way to help a depressed person who is feeling desperate.

The longer-term benefits of ketamine are less clear. Depressive symptoms improved at 24 hours, but not at 25 days in the esketamine group. And the drug's euphoric effects meant that drug-seeking is a likely problem down the road.

The study is a phase 2 proof-of-concept study, too small to have much statistical power. It paves the way for two larger global trials that are now underway. It is published in the American Journal of Psychiatry.