A new study of patients with difficult-to-treat depression has found that psilocybin, the active ingredient in “magic mushrooms,” has the potential to reduce depression.

The study, published Thursday in the New England Journal of Medicine, examined the effects of one of three doses of psilocybin on 233 patients during and after a single six- to eight-hour session.

Hallucinogenic mushrooms, also known informally as “shrooms,” produce hallucinations and associated effects for a few hours, depending on the amount eaten. Although mushrooms can be dried and eaten whole or in capsules, this study used synthetic psilocybin instead.

According to COMPASS Pathways, the company whose synthetic psilocybin the researchers used in the trial, the study is “the largest clinical trial of psilocybin therapy ever conducted.”

233 patients with what is known as treatment-resistant depression were tested. According to the study, 79 patients took the 25mg dose, 75 took the 10mg dose, and 79 took the one-milligram dose.

Within the study, the results of those taking the highest and middle doses were compared with those on the lowest dose. According to the Associated Press, the study had no control group using placebo dummy drugs or standard antidepressants.

Psilocybin was used in conjunction with psychological support and therapy. According to COMPASS pathways, 94% of patients had no experience using psilocybin.

All three groups experienced short-term reductions in depressive symptoms, with the best results in the high-dose group. Results were taken at intervals after the initial psilocybin dose to measure more long-term effects.

Three weeks after dosing, 29.1 percent of the high-dose group showed signs of remission. After three months, the 20 percent high-dose group was still showing signs of continued improvement, according to a COMPASS Pathways release.

“COMP360 psilocybin has a real pharmacological effect … We look forward to launching our Phase 3 program later this year, which will bring us closer to providing COMP360 psilocybin with psychological support for patients who desperately need it. ” said Guy Goodwin, Chief Medical Officer of COMPASS Pathways.

Other scientists confirmed his findings.

Matthew Johnson, professor of psychedelics and consciousness at Johns Hopkins Medicine, told CNN.

Anthony Clare, professor of psychopharmacology at King’s College London, told CNN that “the maximum effect [was] Seen the day after receiving the treatment. This contrasts with standard antidepressants, which take several weeks to reach maximum effect.”

Negative side effects were also found for many patients during their hallucinatory sessions.

“Adverse events occurred in 179 of 233 participants (77%) and included headache, nausea, and dizziness. The Associated Press noted that suicidal ideation or behavior or self-injury occurred in all groups.” has occurred,” the abstract reads, although the latter two symptoms are more common in patients with a history of these behaviors.

According to the Financial Times, one patient fainted due to a “bad trip”.

Some scientists were also skeptical about the trial’s methodology and results.

“There were unequal numbers of severely depressed patients in each group. Clearly with significantly fewer severely depressed people in the ‘effective’ (25mg) dose group,” Professor of Research Methods and Statistics in Educational Psychology at University College London Ravidas told CNN.

COMPASS Pathways is now planning a third phase, which will compare 25 doses with placebo in one trial, and repeatedly dose patients at one milligram, 10mg and 25mg tracks in another.

No trial of psilocybin has ever reached phase III, which is considered the last step before going into an experimental drug before approval by regulators.

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