Ayahuasca, Personality and Acute Psychological Effects in Neo-Shamanic and Religious Settings in Uruguay

The project combined ethnography, chemical profiling and psychometrics. Ethical approval was obtained from the authors' university ethics committee and the national Controlled Substances Division. Data collection occurred at three ceremonies: two neo-shamanic ceremonies in 2019–2020 and one Santo Daime session in October 2021. Questionnaires were completed on paper or online; informed consent and anonymisation procedures followed national requirements. Participants comprised two convenience samples. The Neo-Shamanic Group (n = 26; 16 male, 10 female; mean age 37, range 24–53) attended an eclectic psychotherapeutic centre that offers monthly nocturnal vegetalismo-style ceremonies; six participants reported a prior SUD diagnosis and experience ranged from novices to individuals reporting hundreds of ceremonies. The Santo Daime Group (n = 18; 13 male, 5 female; mean age 42.8, range 18–70) were long-term church members participating in a dance ritual (bailado); reported tenure in the church averaged about 16 years and ceremony counts were much higher (median >400). Two Santo Daime participants did not complete the personality questionnaire and were excluded from ZKAPQ/SF analyses but included in HRS analyses. The groups did not differ significantly in age, sex or education (age t(24.3) = -1.59, p = .125; sex χ2(1) = .17, p = .681; education χ2(2) = 4.39, p = .111). Acute psychological effects were assessed using the Spanish Hallucinogen Rating Scale (HRS), administered within 24 hours of the ceremony. The HRS yields six dimensions: Cognition, Affect, Perception, Somesthesia (bodily sensations), Volition and Intensity; internal consistency was acceptable except for Volition and Intensity. Personality was measured 1–2 weeks post-ceremony with the Spanish short-form Zuckerman-Kuhlman-Aluja Personality Questionnaire (ZKAPQ/SF), which operationalises five traits (Neuroticism-Anxiety, Aggression-Hostility, Sensation Seeking-Impulsivity, Extraversion-Sociability, Activity) each with four facets. Representative ayahuasca samples (one per group) were analysed by quantitative Nuclear Magnetic Resonance (qNMR) following the team’s published PULCON-based protocol: homogenisation, basification and liquid–liquid extraction with ethyl acetate, drying, dissolution in DMSO-d6 and 1H-NMR acquisition using calibrated benzoic acid standard; three analytical replicates were prepared per sample. Individual participant doses were not measured; the investigators estimated intake ranges from observational note: neo-shamanic 20–100 mL (served 1–3 times) and Santo Daime 20–300 mL (served four times during the night). Statistical analyses were performed in R (version 4.0.2). Normality was checked with Shapiro–Wilk tests and homogeneity of variance with Levene’s test. Independent-samples t-tests were used when assumptions held; Wilcoxon Rank Sum tests were used for non-parametric comparisons. Pearson correlations explored associations between the five ZKAPQ traits and the six HRS dimensions. The extracted text indicates some facets violated normality and Levene’s test flagged variance heterogeneity for NE3 and HRS Intensity; the authors adjusted tests accordingly.

Chemical profiling found only DMT and β-carbolines (harmine, tetrahydroharmine, harmaline, harmol) as the main alkaloids in both samples; no adulterants or other alkaloids were detected by 1H‑NMR. The neo-shamanic sample displayed a relatively higher harmine/tetrahydroharmine ratio and a higher β-carbolines:DMT ratio compared with the Santo Daime sample and some prior reports. On personality measures (ZKAPQ/SF), the Santo Daime Group scored significantly lower than the Neo-Shamanic Group on the Neuroticism-Anxiety trait and on several facets: Anxiety (NE1), Dependence (NE3), Low Self‑Esteem (NE4), Anger (AG3) and Restlessness (AC3). The reported differences had medium effect sizes. Two Santo Daime participants were excluded from these personality analyses because they did not complete the questionnaire. Regarding acute effects measured with the HRS, the Neo-Shamanic Group reported significantly higher Somesthesia and Perception scores than the Santo Daime Group, both with medium effect sizes. HRS internal consistency was acceptable except for Volition and Intensity; Levene’s test indicated heterogeneity for Intensity only. Correlation analyses collapsing both groups showed: Sensation Seeking-Impulsivity correlated moderately with Somesthesia (r = .40) and highly with Affect (r = .52); Extraversion-Sociability correlated moderately with Perception (r = .35). When analysed within groups, these associations were present only in the Neo-Shamanic Group: Sensation Seeking-Impulsivity correlated strongly with Somesthesia (r = .54) and Affect (r = .57), and moderately with Perception (r = .39); Extraversion-Sociability correlated moderately with Perception (r = .48). In the Santo Daime Group no significant correlations between personality traits and HRS variables were observed. The investigators note that individual dose was not measured, preventing analyses linking alkaloid intake to subjective effects.

Apud and colleagues interpret the chemical and psychometric results as mutually informative. The detection of only DMT and β‑carbolines in both samples confirms prior findings; the relatively higher β‑carboline content in the neo-shamanic brew may reflect different preparation procedures (for example, prolonged boiling or filtration) and could plausibly contribute to the greater Somesthesia scores in that group. The authors emphasise this link as speculative but draw on pharmacological reasoning: β‑carbolines inhibit MAO‑A and may enhance serotonergic activity, which has been associated with tremor, vomiting and visceral sensations that map onto the HRS Somesthesia dimension. Cultural and ritual differences are central to the authors' interpretation. They characterise the neo-shamanic ceremonies as an "imagistic" mode of religiosity with high-arousal, multisensory stimulation (icaros, percussion, perfumes, tobacco) that may amplify perceptual and somatic experiences, whereas the Santo Daime church exemplifies a "doctrinal" mode with structured liturgy, repetitive hymnody and communal choreography that may reduce emphasis on sensorial peak experiences. This framing supports their hypotheses: higher Somesthesia and Perception in the neo-shamanic group align with an imagistic, high-stimulation ritual, and lower Neuroticism-Anxiety in Santo Daime is consistent with the protective social bonds and stabilising effects often ascribed to structured religious communities. The group-differential correlations between personality and acute effects are also interpreted through setting. The positive associations (particularly between Sensation Seeking-Impulsivity and Somesthesia/Affect) appeared only in the neo-shamanic sample, which the authors argue reflects a more individualistic, exploratory orientation in that setting; by contrast, the communal, rule-bound Santo Daime context may dampen the influence of individual personality on the acute experience. The authors acknowledge key limitations: small sample sizes, heterogeneity in the neo-shamanic group (notably inclusion of participants with SUDs), mixed experience levels across and within groups, potential social desirability bias among committed church members, and inability to measure individual ayahuasca doses. They note these factors may confound personality differences and HRS responses and caution against strong causal conclusions. Finally, they suggest that both pharmacological composition and ritual organisation likely interact to shape acute ayahuasca experiences and that the observed pattern—greater sensory effects and stronger personality–experience associations in an imagistic neo-shamanic setting versus lower neuroticism and weaker personality–experience links in a doctrinal church setting—fits their interdisciplinary data.