As the field of psychedelic-assisted therapy emerges, most data are being captured in controlled clinical research settings. However, most psychedelic use occurs in settings where little reliable data are captured and understood. This project will deepen our understanding of how psychedelic substances affect the brain and body by capturing ecologically valid data at scale in these complex but relevant environments, while maintaining prospective scientific rigor. The project will deliver unique insights for mitigating risk and guiding policy on psychedelic use.