The finding from the National Institute of Mental Health in Bethesda, Md., implicates the brain's glutamatergic system in the development of disease. Little is known about bipolar disorder's neurobiological basis, so targeting the glutamatergic system may lead to better therapies. Current treatments are marked by delayed onset. Most patients do not respond within a week of therapy, causing increased suicide risk.
Participants in the study were assessed using a depression-rating scale before each injection and then at 40, 80, 120 and 230 minutes and one, two, three, seven, 10 and 14 days following.
Researchers found that among 18 patients who were administered ketamine or placebo, those who received ketamine experienced less depressive symptoms compared with those who took placebo. During the course of the trial -- from October 2006 until June 2009 -- 71 percent of participants responded to ketamine and 6 percent responded to placebo.
Bipolar disorder, also known as manic depression, is characterized by extreme mood swings that range from "manic" highs to debilitating lows. Patients usually spend a greater amount of time in depressed states.
About 4 percent of the American population will develop bipolar disorder at some point in their lives.