Variables

Manipulated variables Treatment allocation: Participants were randomised 1:1 to receive a single dose of 25 mg psilocybin or placebo, administered under psychologically supportive conditions. The intervention consisted of five capsules of 5 mg psilocybin, while the placebo consisted of five capsules of inactive placebo (starch 1500). Manipulated variables documentation No files selected. Measured variables Depression severity (MADRS): The Montgomery–Åsberg Depression Rating Scale will be used to assess depressive symptom severity at baseline (V2), 1-week post-dosing (V5), 3-weeks post-dosing (V6), and 6-weeks post-dosing (V7). Total scores will be analysed. Oceanic Boundlessness (OCB): OCB will be derived from the 5-Dimensional Altered States of Consciousness Questionnaire (5D-ASC), administered only at V4, immediately following the acute dosing session. The OCB subscale score will be used, reflecting qualities of the acute psychedelic experience. Subscales of OCB: The 5 OCB subscales, Experience of unity, Spiritual Experience, Blissful State, Insightfulness, and Disembodiment, will be derived from the 5-Dimensional Altered States of Consciousness Questionnaire (5D-ASC) and represent ASC-Subscales 1, 2, 3, 4, and 5, respectively. Connectedness to nature: Connectedness to nature will be assessed using the Connectedness to Nature Scale (CNS), a 14-item Likert scale validated in UK populations. The CNS will be collected at baseline (V2) and at follow-up visits 3 weeks (V6) and 6 weeks (V7) post-dosing. Total scores will be analysed. Missing data Where available, scale-specific missing data guidance will be followed. When guidance is unavailable, missing items will be prorated if no more than 20% of items are missing by replacing missing values with the individual’s mean score for completed items. Unit of analysis All participants with a baseline measurement and at least one post-randomisation outcome measurement will be included. The expected sample size is approximately N = 60. Statistical outliers Outliers will not be removed. Sampling weights Not applicable