Designing evaluation infrastructure for psychedelic harm reduction at events: a methodological framework with formative mixed-methods field application.

Psychedelic and other psychoactive substance use is increasing in non-clinical environments, including music festivals, concerts, and other large-scale gatherings. As psychedelic use expands beyond clinical settings, policymakers, healthcare systems, event operators, and researchers require evidence-informed frameworks for understanding and responding to psychoactive-related distress in naturalistic environments. Despite the growing presence of psychedelic harm reduction services, few studies have established reproducible methods for documenting their operation, coordination with event-health services, or role within triage and escalation pathways in naturalistic settings. This methodological paper proposes an evaluation framework for psychedelic harm reduction services and reports a formative mixed-methods field application involving the Zendo Project at two large-scale events. Nineteen pre-event surveys, five retained post-event surveys, and two matched pre/post records were obtained from medical personnel. Quantitative responses were summarized descriptively, while open-ended responses were used formatively to contextualize and refine the proposed measurement domains. The framework positions psychedelic peer support as a complementary intermediate pathway for medically stable but psychologically distressed individuals, operating alongside rather than in place of medical and public-safety services. The field application identified interpretable measurement domains concerning psychological-distress burden, preparedness, workload, safety, interprofessional coordination, escalation, and attendee disposition. Four respondents completed several principal post-event items and reported favorable perceptions of Zendo's operational role. These responses represent staff perceptions and counterfactual estimates rather than independently verified effects. Beyond evaluating a single intervention, this study offers an initial framework for measuring and comparing non-clinical psychedelic support models and for informing future research, policy development, and event-health infrastructure as psychedelic use continues to expand beyond clinical settings. Additionally, by translating field-based psychedelic support into measurable operational, public health, and economic outcomes, the proposed methodology offers a foundation for the future evaluation, comparison, and development of products, services, and care infrastructures designed to support altered-state experiences in non-clinical environments.