Quality of Acute Psychedelic Experience Predicts Therapeutic Efficacy of Psilocybin for Treatment-Resistant Depression.
Level 4 - case-series / case-control
Uncontrolled open-label trial evaluating within-cohort predictors of response
PubMed 29387009 · doi:10.3389/fphar.2017.00974
What was done
Twenty patients with treatment-resistant depression received two psilocybin dosing sessions (10 mg followed by 25 mg). The Altered States of Consciousness (ASC) questionnaire was administered to evaluate acute subjective dimensions during the 25 mg session, specifically Oceanic Boundlessness (OBN; mystical-type experience) and Dread of Ego Dissolution (DED; anxiety-like experience). Depressive symptoms were measured with the Quick Inventory of Depressive Symptoms (QIDS-SR) at baseline, 1 day, 1 week, and 5 weeks. Repeated-measures ANOVA evaluated OBN-by-Time and DED-by-Time interactions.
What was found
Main effects for the interaction with time on QIDS-SR depressive scores were statistically significant for both OBN (p = 0.002) and DED (p = 0.003), with significant effects at each post-baseline time point compared to baseline. The correlation between OBN and 5-week QIDS-SR scores was significantly specific compared to perceptual dimensions of the ASC (p < 0.05). Numerical values for effect sizes, mean changes, and correlation coefficients were not reported in the abstract.
Why it matters
These findings suggest that the therapeutic efficacy of psilocybin in treatment-resistant depression is linked to the subjective quality of the acute psychedelic experience rather than general perceptual changes.
Limits
The study is constrained by a very small sample size (n = 20), an open-label single-arm design with no control or placebo group, and a lack of longer-term follow-up due to confounding from subsequent treatments. Detailed numerical metrics were not provided in the abstract.