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MDD Symptoms Significantly Reduced With Single, Moderate Psilocybin Dose
A single, moderate dose of psilocybin significantly reduces depressive symptoms in major depressive disorder (MDD) compared to placebo for at least 2 weeks following administration and is well-tolerated, according to a double-blind, randomized clinical trial. The study, recently published in The Lancet’s open-access journal eClinical Medicine, is the first trial to compare a single, moderate dose of psilocybin to a placebo condition.
The findings “demonstrate that the improvements in depressive symptoms shown in previous clinical trials cannot be attributed to the non-pharmacological therapeutic embedding alone,” researchers from the University of Zurich, Sweden, said in the study. “Tolerability of the treatment was favorable in the present trial compared to previously conducted studies using repeated and higher doses.”
Between April 11, 2019, and October 12, 2021, at the psychiatric university hospital in Zurich, Switzerland, 52 patients diagnosed with MDD and no unstable somatic conditions were split into 2 groups. The first group received an oral single, moderate dose (0.215 mg/kg body weight) of psilocybin, and the second group received a placebo. Participants discontinued their psychiatric medication for a minimum of 2 weeks before the study while under the care of a clinician.
Both groups received psychological support throughout the study. After medical screening, all participants completed 2 preparatory visits and 3 integration visits, as well as 60 minutes of psychological counseling during every visit.
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Patients were instructed to “immerse themselves in the experience with an introspective focus” during each drug administration visit, where researchers played a standardized playlist in a “living-room-like environment.” Psychological counseling during administration visits totaled 11 hours: 2 hours of preparation, 6 hours during administration, and 3 hours of integration.
Primary endpoints were defined as changes from baseline 14 days after the intervention. Using the Montgomery-Åsberg Depression Rating Scale (MADRS) and Beck’s Depression Inventory (BDI) scores, researchers assessed depression severity at baseline and the end of the 14 day period.
Participants who received psilocybin showed an absolute decrease in symptom severity of −13.0 points compared to baseline which significantly larger than those who received placebo (95% CI −15.0 to −1.3; Cohens’ d = 0.97; P = 0.0011; MADRS) and −13.2 points (95% CI; −13.4 to −1.3; Cohens’ d = 0.67; P = 0.019; BDI) 14 days after the intervention. Of the participants in the psilocybin condition, 14 out of 26 (54%) met the MADRS remission criteria.
“Treatment response was not associated with the intensity of subjective drug effects, highlighting the need for further investigations into the psychological and neuronal mechanisms of action of psychedelic substances,” researchers concluded. “[M]ore research into the dose-dependent mechanisms of action of psilocybin is needed to optimize the psychological treatment model embedding psilocybin-assisted therapy.”
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