Low Dose Psilocybin Found to Have No Short- or Long-Term Detrimental Effects in Healthy Individuals, Viable for Group Administration


There were no instances of participants withdrawing from the study due to an adverse event caused by psilocybin in the treatment of mental health conditions.

New research has found that 10 mg or 25 mg doses of psilocybin can be safely administered to groups of up to 6 with no negative short- or long-term effects in healthy individuals, according to investigators at the Institute of Psychiatry, Psychology, and Neuroscience at King’s College London.

According to a press release, the findings represent the first step in demonstrating the safety and feasibility of psilocybin as a treatment for a range of mental health conditions, including treatment-resistant depression and post-traumatic stress disorder (PTSD). The researchers noted that psilocybin should be used within controlled settings alongside talking therapy.

“This rigorous study is an important first demonstration that the simultaneous administration of psilocybin can be explored further,” said James Rucker, PhD, lead author of the study, in the press release. “If we think about how psilocybin therapy (if approved) may be delivered in the future, it’s important to demonstrate the feasibility and the safety of giving it to more than 1 person at the same time, so we can think about how we scale up the treatment.”

Current treatment options for conditions such as PTSD are ineffective or partially effective for many patients, resulting in a significant unmet need, according to the study authors. They added that early research suggests that there is potential for psilocybin therapy to treat these individuals, but no trials have been undertaken at the scale necessary for regulatory approval to make the therapy available.

“This therapy has promise for people living with serious mental health problems, like treatment-resistant depression and PTSD,” Rucker said in the press release. “They can be extremely disabling, distressing, and disruptive, but current treatment options for these conditions are ineffective or partially effective for many people.”

In an effort to expand the body of knowledge around psilocybin, the researchers investigated the simultaneous administration of psilocybin in 89 healthy participants with no recent use of the drug. Of those, 60 individuals were randomized to receive either a 10 mg or a 25 mg dose of psilocybin in a controlled environment. The remaining 29 participants acted as the control group and received a placebo, and all participants were provided with 1-to-1 support from trained psychotherapists.

Participants were closely monitored for 6 to 8 hours following administration of psilocybin and were then followed for up to 12 weeks. During this period, they were assessed for multiple potential changes, including sustained attention, memory, and planning, as well as their ability to process emotions.

There were no instances of participants withdrawing from the study due to an adverse event, and no consistent trends suggest that either of the psilocybin dosage strengths had any short- or long-term detrimental effects. The investigators have since completed phase 2 of the study, which explored the efficacy and safety of psilocybin in individuals living with treatment-resistant depression and PTSD. They are currently analyzing the data, according to the press release.

“This study was an early part of our clinical development program for COMP360 psilocybin therapy,” said Guy Goodwin, MD, chief medical officer at COMPASS Pathways, in the press release. “It explored the safety and feasibility of simultaneous psilocybin administration, with 1:1 support, in healthy participants, and provided a strong foundation to which we have now added positive results from our phase IIb trial in 233 patients with [treatment-resistant depression], and from our open-label study of patients taking [selective serotonin reuptake inhibitor] antidepressants alongside psilocybin therapy.”


Psilocybin, in 10mg or 25mg doses, has no short- or long-term detrimental effects in healthy people. News release. EurekAlert; January 4, 2022. Accessed January 4, 2022. https://www.eurekalert.org/news-releases/939161

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