Selection Bias in Psychedelic Research: Comparing Self-Reported Quality-Of-Life Impact Between Enthusiasts and a...

Psychedelic experiences have been associated with improved quality of life, but many studies rely on samples of enthusiasts, raising concerns about selection bias. This study examined whether self-reported quality-of-life impact differed between a convenience sample of psychedelic enthusiasts and a general population sample recruited through Prolific, and whether sample differences persisted after controlling for mindset, setting, motivation, and personality. A total of N = 1,182 participants (N = 583 enthusiasts; N = 599 general sample) with prior psychedelic experience completed an online survey assessing perceived impact, contextual factors, motivation for use, and Big Five personality. Between-group differences were analyzed using Welch's t-tests, Pearson´s chi-squared tests and Mann-Whitney-Wilcoxon tests. A Type III ANCOVA was used to assess whether sample differences in quality-of-life impact remained after controlling for relevant covariates. Enthusiasts reported significantly greater quality-of-life impact (d = 0.84), higher openness, extraversion and agreeableness, more favorable mindsets and settings, and a higher frequency of personal growth motives. In the ANCOVA, sample membership was the strongest predictor of quality-of-life impact, followed by setting, motivation, openness, and mindset. These findings provide empirical clarification of how enthusiast-leaning recruitment strategies can shape reported outcomes in psychedelic research. Results underscore the need to consider sampling frames when interpreting reported benefits and to prioritize representative recruitment in future psychedelic research.