Oct. 11, 2023 – “For people with treatment-resistant depression – so those who have not benefitted from different modes of talk therapy, commonly prescribed antidepressants, or electroconvulsive therapy – 20 percent remission is actually quite good,” lead researcher Professor Colleen Loo says.

“We found that in this trial, ketamine was clearly better than the placebo – with 20 percent reporting they no longer had clinical depression compared with only 2 percent in the placebo group. This is a huge and very obvious difference and brings definitive evidence to the field which only had past smaller trials that compared ketamine with placebo.” The researchers recruited 179 people with treatment-resistant depression. All were given an injection of either a generic form of ketamine that is already widely available in Australia as a drug for anesthesia and sedation – or placebo. Participants received two injections a week in a clinic where they were monitored for around two hours while acute dissociative and sedative effects wore off – usually within the first hour. The treatment ran for a month and participants were asked to assess their mood at the end of the trial and one month later.

As a double-blind trial, neither participants nor researchers administering the drug were aware of which patients received generic ketamine or placebo, to ensure psychological biases were minimized. Importantly, a placebo was chosen that also causes sedation, to improve treatment masking. Midazolam is a sedative normally administered before a general anesthetic, while in many previous studies the placebo was saline.