Previous studies on ketamine infusions to treat depression used saline as a placebo for the control group.
"And there's really not much of a psychological effect, there's really 'no' psychological effect to saline."
That's Dr. Sanjay Mathew of the Debakey VA Medical Center and Baylor College of Medicine. He's the lead author of the most recent study that used midazolam, a short-acting anesthetic which mimics many of the side effects of ketamine.
"And so this study really provided a reasonable test of the hypothesis that ketamine is an anti-depressant above and beyond its psychological effects."
Dr. Mathew says two-thirds of the patients taking ketamine reported a 50 percent reduction in their depression symptoms over 24 hours. And many of the patients continued to benefit from seven days to four weeks after the initial infusion.
"What we think it does is it works on a system in the brain called the glutamate system, which has broad impact on multiple sort-of brain processes, like memory, mood, and emotion."
Some doctors are already prescribing ketamine for off-label use to treat depression. But Dr. Mathew says there are still several years of study ahead to figure the best dosage and time intervals for ketamine treatments.