Turn on, Tune in, and Drop out: Predictors of Attrition in a Prospective Observational Cohort Study on Psychedelic Use

Psychedelic substances such as mescaline, psilocybin and dimethyltryptamine have re-emerged in scientific and public discourse, prompting a parallel rise in naturalistic, web-based prospective studies that collect before-and-after data around planned psychedelic experiences. These designs offer ecological validity, efficient recruitment and low cost, but they lack experimental control and are vulnerable to self-selection and high attrition, which can introduce systematic bias and threaten the interpretability of results. Hübner and colleagues used data from a previously published prospective cohort of psychedelic users to investigate predictors of study noncompletion. Their specific interest was whether baseline positive attitudes toward psychedelics or the intensity of challenging acute experiences predicted dropout, alongside demographic and psychological factors that prior longitudinal research in other domains has linked to attrition (for example, younger age, lower education, unemployment, poorer mental health and low conscientiousness). The analysis was exploratory and aimed to quantify which variables most strongly associated with nonresponse at the key 4-week endpoint.

Data were drawn from a convenience sample recruited online via social media to the PsychedelicSurvey platform; informed consent was obtained electronically. The design was a naturalistic, prospective cohort in which participants completed surveys at multiple timepoints surrounding a planned psychedelic experience: baseline 1 week before (timepoint 1), preacute 1 day before (timepoint 2), postacute 1 day after (timepoint 3), a 2-week follow-up (timepoint 4) and the key 4-week follow-up (timepoint 5). Attrition was defined as failure to complete the key 4-week endpoint; completers were those who reached that endpoint even if they missed earlier surveys. Baseline measures included demographics (age, gender, education, employment) and a battery of trait and mental-health scales: the Warwick-Edinburgh Mental Well-being Scale (WEMWBS), the 10-Item Personality Inventory (big five traits), Social Connectedness Scale, a modified Tellegen Absorption Scale, the short Spielberger State-Trait Anxiety Inventory (STAI-SF), the Quick Inventory of Depressive Symptomatology (QIDS), the Suicidal Ideation Attributes Scale (SIDAS) and Peters' Delusional Inventory (PDI). A four-item self-constructed ‘‘psychedelic advocacy’’ score (α=.78) measured baseline pro-psychedelic attitudes and experience. Postacute surveys (1 day after the experience) assessed subjective drug effects using subscales and instruments such as the visual effects (VE) subscale of the 11-dimension Altered States of Consciousness questionnaire, the Mystical Experience Questionnaire, the Challenging Experience Questionnaire, the Ego Dissolution Inventory, the Emotional Breakthrough Inventory and a Physical Symptoms Inventory. Outcome measures (WEMWBS, absorption, QIDS, STAI-SF, PDI) were re-assessed at 2 and 4 weeks. Statistical analysis used logistic regression to predict the binary outcome of attrition versus completion at 4 weeks. Four models were fitted: two baseline models (one with demographic predictors and one with psychological measures), one model with postacute psychedelic-effect measures, and one model incorporating change scores (2-week minus baseline) alongside baseline values for key outcomes. Categorical references were set to Male for gender and to secondary education for education level; employment status was omitted from the demographics model because of correlation with education. Analyses were performed in R (version 3.6.1).

Across timepoints the numbers of respondents were 564, 535, 379, 315 and 212 at timepoints 1–5 respectively, yielding an overall pool of 741 participants who responded at any point. Of these, 529 (71.4%) dropped out by the key 4-week endpoint and 212 (28.6%) completed it. Dropout timing varied significantly: 170 (22.9%) stopped before the preacute timepoint, 139 (18.8%) stopped after the experience (postacute), 89 (12.0%) stopped at the 2-week follow-up and 131 (17.7%) stopped at the 4-week endpoint (χ²4=56.89; P<.001). More noncompleters left prior to the postacute timepoint than afterwards (309, 58.4% vs 220, 41.6%; χ²1=29.28; P<.001). Logistic regression identified several baseline predictors. Age was associated with lower odds of dropout (β=-0.024; P=.007), meaning older participants were more likely to complete the study. Educational differences were significant: participants with a university degree were less likely to drop out than those with secondary education (β=-0.574; P=.005), and those with primary education were also less likely to drop out than those with secondary education (β=-0.876; P=.008). Among personality traits, higher extraversion predicted increased probability of dropping out (β=0.082; P=.012), whereas higher conscientiousness predicted reduced probability of dropout (β=-0.079; P=.024). All other tested variables were nonsignificant predictors, including baseline psychedelic advocacy, measures of acute subjective experience (including challenging experiences), suicidality, delusional thinking, physical side effects, and psychedelic-induced changes on outcome measures between baseline and 2 weeks.

Hübner and colleagues interpret their findings as indicating that attrition in web-based prospective studies on naturalistic psychedelic use is driven largely by demographic and personality factors that mirror patterns observed in other longitudinal research domains. Specifically, younger age, secondary education level and the combination of high extraversion with low conscientiousness were associated with higher dropout risk. The authors note that conscientiousness—conceptualised as the tendency to follow norms, be planful and persist with obligations—may explain why more conscientious participants were likelier to complete follow-ups. Importantly, no evidence was found that psychedelic-specific variables biased retention: neither baseline pro-psychedelic advocacy nor the quality or difficulty of acute psychedelic experiences predicted noncompletion, nor did observed psychological changes after use predict attrition. The researchers suggest this reduces some concerns that naturalistic psychedelic studies are systematically skewed toward favourable responders or that adverse experiences drive dropout in ways that would distort outcome estimates. The authors discuss plausible pragmatic explanations for early dropout, such as limited access to surveys around the time of taking a substance (for example at festivals), postponement or nonperformance of the planned experience, and decayed motivation. They also remark that predictors may differ for early versus late dropouts and that targeted retention strategies (mobile reminders, brief follow-ups, incentives, gamification or participant communities) used in other fields might be applicable here. Acknowledged limitations include the inability to observe outcomes among early nonresponders—so rare but extreme adverse reactions could have been missed—and the self-selected nature of the sample (predominantly young, male, highly educated and pro-psychedelic), which limits generalisability. The authors further note cross-study variability in definitions and measures of attrition, which complicates comparisons across disciplines. They recommend future work that obtains minimal data from nonresponders (with prior consent) and specifically investigates outlier adverse events.

The study concludes that, in this prospective observational cohort, the strongest predictors of attrition were general demographic and personality variables—age, educational level and conscientiousness/extraversion—whereas psychedelic-specific factors were poor predictors. Hübner and colleagues suggest that retention-improving methods validated in other research fields are likely transferable to web-based psychedelic studies and that, despite limitations, large-scale prospective online data collection can yield reasonably reliable information on predictors and processes of change related to psychedelic use.