Examining changes in personality following shamanic ceremonial use of ayahuasca

Weiss and colleagues situate their study against renewed scientific and public interest in psychedelics, noting two parallel strands of work: laboratory-based clinical research on serotonergic psychedelics (e.g., psilocybin, LSD) and naturalistic investigations of shamanic medicines such as ayahuasca. They highlight prior, mixed evidence that single or short-course psychedelic experiences can sometimes produce durable changes on Five-Factor Model (FFM) personality traits—particularly decreases in Neuroticism and increases in Openness and Extraversion—but note methodological limitations in earlier work (small samples, lack of informant corroboration, few control conditions, and limited investigation of moderators). The ceremonial context of ayahuasca is emphasised as a potentially active element, encompassing group formats, shamanic guidance (e.g., icaro chants), purgative processes, and an ontological framework that frames healing in spiritual terms. The study’s primary aim was to prospectively examine personality change following ceremonial ayahuasca use and to test moderators of change. Specifically, the investigators assessed self- and informant-reported FFM traits at Baseline, immediately Post-retreat, and at a 3-month Follow-up, expecting decreases in Neuroticism and increases in Openness and Extraversion, and hypothesising that mystical-type experiences would amplify increases in Openness. They also aimed to evaluate the roles of predisposing characteristics (demographics, baseline personality), acute experiential variables (mystical-type states, reappraisal, discomfort), and ceremony-specific elements (purgative experiences, perceptions of the shaman and ritual) as moderators of any observed personality change.

This was a prospective, naturalistic study of participants attending ayahuasca retreat centres. Recruitment occurred at three shamanic centres in South and Central America (Arkana, Soltara, La Medicina). Of 330 recruits, after validity screening and exclusions for inadequate responding, the final analytic sample comprised 256 participants who provided complete self-report data at Baseline, Post-retreat, and 3-month Follow-up (mean age 34.8, 161 males, 94 females). Informant-report data (IPIP-NEO-60) were available for 110 participants (informants provided Baseline and Follow-up reports). The investigators note that because the study was naturalistic they did not implement a placebo or blinded control condition. Personality was measured with validated instruments: self-reported FFM traits via the IPIP-NEO-120 and informant-reported traits via the IPIP-NEO-60. Acute experiential measures included the Revised Mystical Experience Questionnaire (RMEQ), the Ego Dissolution Inventory (EDI), and a novel Ayahuasca Experience Inventory (AEI) developed by the authors to capture Clarity, Reappraisal, and Discomfort. Additional bespoke scales assessed suggestibility (MISS), expectancies about personality/psychopathology change, over-reporting of low-base-rate phenomena, and perceptions of shamanic elements and purgative experiences. Ceremony characteristics (number of ceremonies, retreat length, approximate dosing in glasses, and concurrent use of other plant medicines) were also recorded. The analytic plan used linear mixed models (equivalent to repeated-measures ANOVA) to test changes across timepoints and to test moderation by five sets of variables: validity indicators (expectancy, suggestibility), participant characteristics (demographics, lifetime psychedelic use), baseline personality scores, acute experience elements (factor-analysed into a Mystical factor and an AEI Discomfort factor), and ceremony variables (ceremony characteristics and shamanic perceptions). Moderation tests entered each moderator as a fixed covariate interacting with time. The investigators preregistered hypotheses and analyses, reported two deviations in supplementary methods, and set a stricter significance threshold of p < .01 for omnibus moderation tests (p < .05 for preregistered hypotheses). Post-hoc power analyses indicated the self-report sample was well powered to detect small time effects and small interaction effects; informant analyses had less power for small effects but sufficient power for small-to-medium effects. Multiple validity checks were applied: participants endorsing improbable experiences or high invalidity on psychopathy-based validity scales were excluded or had data removed for specific measures. Expectancy and suggestibility were explicitly measured and included in moderation analyses to address demand and placebo concerns. Where factor reduction was needed among experiential measures, exploratory factor analyses produced a primary Mystical factor (encompassing RMEQ subscales, EDI, AEI Clarity/Reappraisal) and a distinct AEI Discomfort factor.

The most robust and consistent finding was a substantial decrease in Neuroticism following retreat. Self-report effect-size estimates indicated a large within-subject change immediately post-retreat (dz T1–T2 ≈ -1.00) and a substantial reduction remaining at 3 months (dz T1–T3 ≈ -0.85). When expressed as change in trait scores relative to baseline variance, the authors report declines of about 0.62 standard deviations (ds) from baseline to Post and about 0.53 ds from baseline to 3 months; informant-report data corroborated the decline at 3 months (F[1,109] = 42.45, p < .0001; B = -0.35, 95% CI [-0.45, -0.24]; dz = -0.62). Other domain changes were less consistent. Informant-report indicated a small increase in Openness at 3 months (F[1,109] = 4.61, p = .03; B = 0.09, 95% CI [0.01, 0.17]; dz = 0.20), while self-report analyses showed some short-term increases in Extraversion and Conscientiousness immediately post-retreat (e.g., Conscientiousness B = 0.17, 99% CI [0.11, 0.23], dz = 0.48), but Conscientiousness declined somewhat by 3 months relative to the immediate post-retreat level (B = -0.07, 99% CI [-0.11, -0.02], dz = -0.22). The investigators conclude that hypotheses for robust Openness and Extraversion increases were not consistently supported once expectancy and suggestibility were accounted for, and note elevated baseline Openness in the sample may have constrained upward change. Moderator analyses identified several patterns. Expectancies for favourable change and higher trait suggestibility were associated with amplified changes in Neuroticism, Extraversion, and Conscientiousness; however, when analyses were restricted to participants denying expectancies and those with low suggestibility, significant reductions in Neuroticism persisted in both self- and informant-report data (e.g., dz self T1–T3 ≈ -0.59 among those denying expectancy). Baseline personality strongly moderated change: individuals higher in Neuroticism and lower in the other adaptive traits tended to show the largest adaptive shifts, though the authors note regression to the mean as a potential partial explanation and report sensitivity tests excluding extreme baseline scorers that did not materially alter the Neuroticism, Extraversion, Agreeableness, and Conscientiousness interaction patterns. Acute experiential moderators were salient. A composite Mystical factor (capturing unitive, insightful, awe-related, and reappraisal elements) amplified decreases in Neuroticism (one-standard-deviation increase in Mystical: B = -0.15 post-ceremony, B = -0.10 at Follow-up) and amplified immediate increases in Extraversion, Openness, Agreeableness, and Conscientiousness. AEI Reappraisal—reflecting introspective cognitive reappraisal and meaning-making during ceremony—was the strongest specific moderator of long-term reductions in Neuroticism (B T1–T3 = -0.21). Some ceremony- and purging-related perceptions (e.g., experiencing the decoction as medicinal, feeling purging was complete) were also associated with larger adaptive changes, though these effects were generally weaker and not consistently supported in the smaller informant sample. The authors report no major safety/adverse-event data in the extracted text. Attrition and sample composition details: 256 participants provided full self-report data, and 110 had informant reports; demographics and power analyses are described to support interpretation.

Weiss and colleagues interpret their findings as preliminary evidence that attendance at ayahuasca ceremony is associated with appreciable reductions in Neuroticism that are observable to outside informants and persist for at least three months. They emphasise the magnitude of the Neuroticism change, noting it is comparable to typical pre–post effects reported in large meta-analyses of psychological interventions and to reductions seen in some clinical psychedelic trials. The investigators stress that mystical-type experiences and in-ceremony reappraisal processes appear to potentiate adaptive change, suggesting mechanistic overlap with psychotherapeutic processes (e.g., cognitive reappraisal, meaning-making). Baseline personality emerged as an important moderator: participants with less adaptive baseline profiles (higher Neuroticism; lower Extraversion, Openness, Agreeableness, Conscientiousness) tended to show larger adaptive shifts. The authors acknowledge significant limitations that constrain causal inference. The naturalistic design precluded placebo control and blinding, leaving open the possibility that non-pharmacological aspects of retreat attendance (expectancy, demand characteristics, the retreat context itself) contributed to observed change. To mitigate these threats they measured and modelled expectancies and suggestibility, excluded invalid responders, used immediate and delayed follow-ups, and incorporated informant reports; nevertheless, they concede that some degree of expectancy or Hawthorne-like influence cannot be ruled out. Additional limitations cited include sample non-representativeness (elevated baseline Openness), potential bias from incentivising a small number of participants to reduce attrition (N = 6), and the need for longer-term follow-up to determine durability of effects. In terms of implications, the investigators propose that ceremonial ayahuasca contexts may contain elements—music, guided presence, communal format, shamanic practices, purgative ritual—that parallel and potentially augment components of established psychedelic-assisted therapy protocols. They recommend future well-powered studies with preregistered moderation tests, samples with lower adaptive trait levels if clinical effects on internalising psychopathology are of interest, and continued use of informant-report measures to reduce reliance on self-report alone. The authors stop short of causal claims beyond the observational scope of their design and note the need for controlled trials to disentangle pharmacological effects from contextual, expectancy, and selection factors.

In conclusion, the study reports that attending ayahuasca ceremony was associated with a medium-sized decrease in Neuroticism that was evident in both self- and informant-reports and persisted at three months. Baseline personality, mystical-type experiences, in-ceremony meta-cognitive reappraisal, and some shamanic and purgative elements predicted greater adaptive personality change. The authors suggest these attributes of ayahuasca ceremony may have therapeutic relevance for neuroticism and internalising psychopathology, particularly among individuals with elevated baseline neuroticism, and they call for further controlled, well-powered research to confirm and extend these findings.