A large Phase 2 trial of psilocybin, the psychoactive ingredient in magic mushrooms, found that it was effective at reducing symptoms of depression in participants—findings that add to a growing body of research into the use of psychedelic drugs to treat mental health conditions.

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A growing interest in psychedelics to treat mental health conditions

According to Vox, there has been a growing interest in using psychedelic drugs to treat mental health conditions, such as depression, anxiety, and PTSD—and several small studies suggest psychedelics can be beneficial for patients.

For example, a study by researchers at Johns Hopkins University (JHU) found that psilocybin reduced depression and anxiety in patients with life-threatening cancer.

Another study published in JAMA Psychiatry found that psilocybin was more effective at treating depression than typical antidepressant medications, NPR reports. "The effect was more than four times greater," said Alan Davis, one of the study's authors and a faculty member at both JHU and Ohio State University.

Compass Pathways conducts the largest clinical trial of psilocybin

Compass Pathways, the second-largest psychedelics company in the world, on Tuesday announced the results of a Phase 2b trial that tested synthetic psilocybin for treatment-resistant depression. According to STAT News, this is currently the largest randomized, controlled, double-blind trial of psilocybin so far.

The trial included 233 participants across 10 countries in North America and Europe. The participants were divided into three groups and received either 25 milligrams, 10 milligrams, or one milligram of synthetic psilocybin. All participants also received therapy alongside the medication.

The participants were followed for 12 weeks and the severity of their depression was assessed using the Montgomery-Asberg Depression Rating Scale (MADRS), a diagnostic questionnaire used by psychiatrists.

According to the company, participants who received the highest dose of psilocybin (25 milligrams) saw a significant decrease in depressive symptoms compared to participants who received the lowest dose. Specifically, 29.1% of participants in the highest-dose group were in remission after three weeks, compared to 7.6% in the lowest-dose group. And around a quarter of patients in the highest-dose group were still in remission three months after treatment, compared with 10.1% of patients in the lowest-dose group.

In addition, participants who received the highest dose of psilocybin reduced their MADRS scores by an average of 6.6 points more than participants in the lowest-dose group.

Overall, more than 90% of the participants experienced mild to moderate side effects, including headache, nausea, fatigue, and insomnia. However, 12 participants reported more severe side effects, such as suicidal behavior, intentional self-injury, and suicidal ideation.

According to Lars Christian Wilde, Compass' co-founder and president, suicidal ideation or behavior is common among depressed patients. "We're dealing with a severe patient population, both in terms of patient severity and duration of their depressive episode," he said. "Unfortunately, those events have to be expected."

What's next for Compass and its psilocybin treatment?

"Everyone agrees such a result hasn't been seen before in depression research, so we're incredibly happy with that result," Wilde said.

Separately, Boris Heifets, a neuroscience researcher at Stanford University who was not part of the study, said the results were "super promising." And while he noted that detailed data from the study was not yet available, he said the summary results were "pretty good news."

FDA has already designated Compass' psilocybin medication a "breakthrough therapy," STAT News reports, which means its drug approval process could be accelerated if trials continue to show positive results.

According to Wilde, the company plans to begin a larger Phase 3 trial of the drug by mid-2022 and will seek final regulatory approval after that. "Our goal is still to be ready for approval by the end of 2024 or 2025 in North America and Europe," he said. (Flanagan/Kary, Bloomberg, 11/9; Lee, Business Insider, 11/9; Goldhill, STAT News, 11/9; Hamilton, “Shots”, NPR, 11/4; Heilweil, "Recode," Vox, 10/13)