TORONTO — Greg Rennie says his bipolar depression was an eight out of 10 when he went in for his first ketamine infusion in April 2025.

He ranked it a zero out of 10 right afterward.

Rennie, who has had bipolar depression for almost 30 years, was one of the 68 participants in a University Health Network clinical trial evaluating the safety and effectiveness of repeated ketamine infusions for people with bipolar depression.

The 61-year-old was hooked up to an IV in a UHN hospital room. About 10 minutes after they turned on the ketamine he recalls feeling like he was floating, dissociated from his body, like he was in outer space. He began to envision himself in a dark room where at times light would shine through.

“I realized what it was showing me is that this is your depression. That I’m in this black box,” he said.

“It did change my life in the way that it made me realize how dark the depression is and that a lot of the time I live within this black room.”

Rennie wasn’t the only one who found his symptoms improved.

The clinical trial, published in JAMA Psychiatry Wednesday, found the treatment reduced depressive symptoms for more than 35 per cent of participants, who received two 40-minute ketamine infusions over two weeks.

That’s compared with fewer than 12 per cent in the control group receiving a benzodiazepine medication as a comparison.

Psychiatrist and senior author Dr. Joshua Rosenblat said the ketamine infusions also didn’t trigger mania, psychosis or suicidality.

“That’s one of the most important takeaways, that it didn’t trigger mania, which is what a lot of people were concerned about,” Rosenblat said.

“What we found was that with each subsequent dose there were more and more benefits,” Rosenblat said.

People with bipolar depression have often been excluded from ketamine treatment due to the risk of bringing on a “switch” from depression to mania, said Dr. Jennifer Swainson, a psychiatrist in Edmonton who was not involved in the study.

“This randomized controlled trial suggests that this is not a significant concern, not more so than we may see with the course of the illness itself,” Swainson said.

Ketamine, an anesthetic used for decades to block pain during surgery, has been offered in small doses to treat severe depression, and other psychiatric disorders, over the past 20 years.

There is a need for a treatment that works for bipolar depression, as about one in three do not respond to standard treatments and many medications make people feel worse, Rosenblat said. Approximately three per cent of people in Canada will experience bipolar disorder, according to the federal government’s latest statistics.

There have been concerns about the risk of ketamine treatment leading to addiction in the wake of Matthew Perry’s overdose death. The former “Friends” star was receiving legitimate ketamine infusion treatments for depression but turned to a dealer for supplying him with illicit doses, according to court filings.

However, research shows that most people using ketamine for depression are not at high risk of abusing it or developing an addiction, Swainson said. In her experience of treating patients with ketamine for depression, she said many reported a neutral opinion or even a dislike of the drug’s effects, but kept using it as prescribed because it helped.

The barrier to ketamine treatment becoming more widely accessible is it’s not covered by most provincial health insurance. Some clinics cover the cost of a limited number of sessions or suggest patients join clinical trials like this one to get access to it. There are also private community clinics that offer treatment that can cost $4,200 for a full cycle of six treatments.

The study found patients’ symptoms returned after they stopped the infusions, suggesting they would need maintenance sessions to keep up the antidepressant effects.

That’s what Rennie has done. He was referred to a private clinic, where he gets infusions every couple months, for $500 for a session.

“That’s the sad part of it,” said Rennie, who believes the therapy should be covered and available across Canada. “I think that has to change.”

This report by The Canadian Press was first published Sept. 2, 2026.

Canadian Press health coverage receives support through a partnership with the Canadian Medical Association. CP is solely responsible for this content.