Altered States of Consciousness During Ceremonial San Pedro Use

Bohn and colleagues situate San Pedro (Echinopsis pachanoi), a mescaline-containing cactus with a long Andean ceremonial history, within the recent rise of Western ceremonial use and note a striking absence of psychological research focused exclusively on its subjective effects. Earlier work on classical serotonergic psychedelics has linked altered states of consciousness (ASC), mystical-type experiences and ego-dissolution to therapeutic outcomes, while also recognising that challenging experiences can cause harm; the authors highlight that San Pedro contains mescaline plus a range of other alkaloids that may produce both serotonergic and sympathomimetic effects, potentially shaping a distinct ASC profile. They further emphasise that set and setting, including ceremonial guidance, are likely to influence subjective reports, complicating attributions solely to the drug. The study sets out to provide a first observational characterisation of consciousness changes during ceremonial San Pedro use. Specifically, the investigators aimed to: (1) determine whether ceremonial San Pedro consumption produces ASC that differ from normal waking consciousness; (2) construct a consciousness profile by comparing relative strengths of different ASC dimensions; and (3) identify which ASC co-occur during San Pedro experiences. Given San Pedro’s history and its pharmacology, the authors expected overall psychedelic-like effects but did not make specific predictions about the relative patterning of ASC across subscales or their interrelations.

This was an observational study of participants attending guided San Pedro ceremonies offered by four organisations in the Netherlands between July 2019 and March 2020. Individuals self-enrolled in ceremonies; the researchers were not involved in running them. Recruitment occurred via the organisations, with interested attendees invited to complete online surveys pre-ceremony (baseline), immediately post-ceremony (the data used here) and at 4-week follow-up. Participants provided informed consent; the study received university ethics approval. Forty-two people completed the post-ceremony survey. Demographic data were available for 36 of these: an equal split of 18 women and 18 men, mean ages about 44.7 years, most with at least vocational or higher education, and 94% reporting prior experience with entheogens. Exclusion criteria applied by facilitators included psychopharmacological medication, psychotic-spectrum vulnerabilities, substance addiction, pregnancy, cardiovascular issues, epilepsy and other medical contraindications; the researchers additionally excluded non-fluent Dutch speakers and those under 18. Subjective effects during the ceremony were measured with four psychometric instruments translated into Dutch (non-validated translations): the 11D-ASC (42 items across 11 subscales) to capture broad ASC dimensions; the Ego-Dissolution Inventory (EDI; 8 items); the Challenging Experience Questionnaire (CEQ; 26 items with seven subscales) to assess adverse affective/cognitive reactions; and the Mystical Experience Questionnaire (MEQ; 30 items with four subscales). Internal consistency (Cronbach's alpha) for all scales and subscales was reported as sufficient to excellent. The authors also collected descriptive information about ceremonial context based on site visits and observations, noting variability in preparation, dosing practices, group size (7–20), rituals, music and ancillary substances (e.g. mapacho tobacco, sometimes cannabis). Data analysis aggregated item scores into subscale means. Four missing CEQ item responses were incorporated into average subscale scores; no other missing data were present. To test aim 1, one-sample t-tests compared 11D-ASC subscales and EDI scores against zero (the questionnaires’ sober-state baseline). For aim 2, within-subjects ANOVA with Bonferroni-corrected pairwise comparisons contrasted subscale means for the 11D-ASC (including EDI), and separate repeated-measures ANOVAs were run for MEQ and CEQ subscales. For aim 3, Pearson correlations (Bonferroni-corrected) among subscale totals were computed and visualised via hierarchical clustering (corrplot in R) and a network analysis (MATLAB graph function), with network clusters interpreted as patterns of interrelation rather than causal links.

Forty-two participants completed the post-ceremony survey; demographic details were available for 36. Internal consistency for the translated scales was reported as adequate to excellent. Four CEQ item responses were missing and included in subscale averages; no other missing data were noted. Addressing the first aim, one-sample t-tests showed that all 11D-ASC subscales differed significantly from zero, indicating that participants experienced departures from normal waking consciousness on each measured ASC dimension. Ego-dissolution (EDI) was also significantly above zero; the mean EDI score was 47.85 (SD = 26.17), denoting a medium level of ego-dissolution on the instrument’s scale. On the MEQ, 26 participants (62% of the sample) met the predefined criterion for a “complete mystical experience” (total score > 3.0, i.e. >60% of the maximum). The CEQ yielded a relatively low overall mean challenging-experience score of 0.20 (SD = 0.19) on the scaled metric used; at the individual level, four participants showed slight-to-moderate CEQ scores, one participant scored between moderate and strong, and one participant scored between strong and extreme. For the second aim, a within-subjects ANOVA comparing 11D-ASC subscales plus EDI was significant (F(11,31) = 10.156, p < .001, partial η2 = .783), indicating heterogeneity in the strength of different ASC dimensions. Spiritual experience was the highest-scoring domain (above 63). A medium-scoring cluster (means 43–54) included Experience of unity, Blissful state, Insightfulness, Complex imagery, Elementary imagery, Changed meaning of percepts and Ego-dissolution; scores among these were not statistically different from one another. A low-scoring cluster (means 10–23) comprised Disembodiment, Impaired control and cognition, and Anxiety; these were significantly lower than the medium group. Audio-visual synesthesia (mean ≈ 37) lay between the groups. MEQ subscales differed overall (F(3,39) = 7.786, p < .001, partial η2 = .375), with Transcendence of time and space notably lower than the other MEQ factors; the authors further identified that transcendence of space specifically scored lower than the other MEQ components. CEQ subscales also differed (F(6,36) = 11.603, p < .001, partial η2 = .659), with Grief and Physical distress most pronounced and not significantly different from each other, while Fear, Insanity, Isolation, Death and Paranoia clustered at lower levels. For the third aim, correlation and network analyses revealed two distinct clusters. The first cluster grouped MEQ subscales, the EDI, and several ASC subscales (Experience of unity, Spirituality, Blissfulness, Insightfulness, Disembodiment, Elementary and Complex imagery, Audio-visual synesthesia, Changed meaning of percepts), interpreted as positively valenced or desirable states. The second cluster comprised all CEQ subscales and ASC subscales linked to Anxiety and Impaired control and cognition, interpreted as negatively valenced states. After correction for multiple comparisons there were no significant correlations between the two clusters, and no significant negative correlations across clusters, suggesting that positive and negative ASC tended to co-occur within their own networks but were not mutually exclusive in this sample.

Bohn and colleagues interpret their observations as providing tentative evidence that ceremonial San Pedro use produces broad, psychedelic-like alterations in consciousness. They note that significant departures from sober-state scores across all 11D-ASC dimensions, medium levels of ego-dissolution, and a 62% prevalence of complete mystical experiences collectively support the characterisation of San Pedro as a psychedelic in ceremonial contexts. The authors also highlight that Spiritual experience scored highest among ASC dimensions, but they caution that ceremonial elements — rituals, music, preparatory instructions and facilitator framing — may have amplified spiritual reports. The discussion emphasises the distinctive profile that emerged: relatively strong spirituality, moderate imagery, unity, insight and ego-dissolution, but comparatively low disembodiment, anxiety and impaired control. The authors suggest that sympathomimetic and entactogenic properties of San Pedro’s alkaloid mix (e.g. adrenergic and dopaminergic activity) could increase bodily arousal and physical awareness, which may reduce disembodiment and spatial transcendence while elevating physical distress in cases of challenging experiences. Grief emerged as a prominent dimension among negative responses, a pattern the authors attribute in part to the therapeutic framing of ceremonies that invites autobiographical emotional processing. On co-occurrence, the investigators report two largely separate networks of positive and negative states; ego-dissolution was central to the positive/mystical cluster, while anxiety and impaired cognition anchored the negative cluster. They note that negative affective states may induce a downward bias that amplifies other negative experiences, but that positive and negative experiences were not inversely related in their data, implying they can co-exist during a single extended psychedelic episode. The authors acknowledge several limitations: the observational naturalistic design without placebo or control conditions precludes separation of drug effects from setting or expectancy; small sample size and limited number of organisations reduce generalisability; the dose and alkaloid content of consumed San Pedro preparations were uncontrolled and unknown; some ceremonies permitted adjunctive substances (mapacho, cannabis) complicating attribution; and the Dutch translations of scales were non-validated. They recommend replication with larger samples, controlled dosing, direct substance comparisons and designs that disentangle the contributions of set and setting to subjective effects. Overall, the authors present these findings as a descriptive starting point for further research into the physiology and psychology of San Pedro-induced altered states.

The authors conclude that, within the limitations of an observational design, ceremonial San Pedro use is associated with widespread changes in consciousness comparable to those reported for classical psychedelics. Their data indicate particularly strong spiritual experiences alongside moderate levels of insight, bliss, unity, ego-dissolution and imagery, and relatively low levels of disembodiment, impaired cognition and anxiety. Finally, positively valenced ASC tended to cluster together and negatively valenced ASC clustered separately, though both positive and negative experiences can occur within the same ceremony; the findings are offered as an initial characterisation to inform future controlled and clinical research on San Pedro.