Personality, Psychopathology, Life Attitudes and Neuropsychological Performance among Ritual Users of Ayahuasca: A Longitudinal Study

Ayahuasca is a traditional Amazonian psychoactive brew containing N,N-dimethyltryptamine (DMT) together with monoamine-oxidase inhibiting harmala alkaloids, which make DMT orally active. Acute administration produces marked alterations in perception, thought and emotion and increases blood flow in frontal and paralimbic brain regions, but prior neuroimaging did not show activation of classic reward structures implicated in addiction. Although previous, generally small studies have not detected clear long-term neuropsychological or psychopathological harm in ritual ayahuasca users, rising numbers of regular users and public health concerns motivate a more systematic evaluation of personality, mental health, life attitudes and cognitive function in long-term ritual contexts. Bouso and colleagues set out to examine these domains in a comparatively large sample of ritual ayahuasca users and matched non-using controls, with assessments at baseline and approximately one year later. The study aimed to determine whether long-term, regular ritual use is associated with maladaptive personality traits, increased psychopathology, or cognitive deficits, and to assess measures of spirituality and psychosocial well-being in this population.

The investigators recruited ritual ayahuasca users from two Brazilian samples: a rural 'Jungle' community affiliated with CEFLURIS (56 users) and an urban group from the Barquinha church in Rio Branco (71 users). Inclusion required at least 15 years of ayahuasca use with a minimum frequency of twice per month. Comparison subjects were matched for age, sex and years of education and were active in non-ayahuasca religious practice; controls were excluded if they had taken ayahuasca more than five times. Baseline sample sizes were 56 users and 56 controls in the Jungle sample, and 71 users and 59 controls in the Urban sample. Follow-up assessments were carried out 8–12 months later, though attrition reduced the numbers available for some tests. A broad battery of self-report instruments and neuropsychological tests was administered. Personality was measured with the Temperament and Character Inventory (TCI). Psychopathology was assessed using the Symptom Checklist-90-Revised (SCL-90-R). Cognitive and executive functions were tested with the Stroop Color and Word Test, the Wisconsin Card Sorting Test (WCST), and the Letter-Number Sequencing (LNS) subtest from the WAIS-III; everyday frontal-lobe related behaviours were measured with the Frontal Systems Behaviour Scale (FrSBe). Life attitudes and psychosocial well-being were evaluated with the Spiritual Orientation Inventory (SOI), the Purpose in Life Test (PLT), and the BIEPS psychosocial well-being scale. Brazilian Portuguese adaptations of the instruments were used when available. Because of missing data at follow-up and some test loss in field conditions, analyses used all available data per test rather than a single complete-case sample. For each outcome the team performed two-way analyses of variance (ANOVA) with between-subjects factors Group (ayahuasca users vs controls) and Sample (Jungle vs Urban), analysing first-assessment and second-assessment data separately. Results were considered significant at p<0.05. The study adhered to the Declaration of Helsinki and received local ethics approval; all participants provided informed consent.

Sociodemographics: At baseline there were no significant differences between users and controls in age, sex, years of education or income in either the Jungle or Urban samples. Some employment-status differences were noted in the Jungle sample, with controls classified as more qualified by Hollingshead categories. Follow-up retained 88 Jungle participants (39 users, 49 controls) and 58 Urban participants (39 users, 19 controls). Personality (TCI): In the first assessment ayahuasca users showed significantly lower Harm Avoidance (HA) [F(1,223)=17.73; p<0.001] and higher Reward Dependence (RD) [F(1,223)=6.98; p=0.009] relative to controls. No overall group difference was observed for Novelty Seeking or Persistence, though a trend for a Group×Sample interaction on Persistence was reported. For character dimensions, users scored lower on Self-Directedness (SD) [F(1,223)=9.56; p=0.002] and higher on Self-Transcendence (ST). The SD effect was driven by lower Responsibility [F(1,116)=24.75; p<0.001] and lower Self-Acceptance [F(1,116)=12.23; p=0.001]. Subscales contributing to higher RD and ST included Attachment/Dependence and Transpersonal Identification and Spiritual Acceptance, respectively. These personality differences were generally maintained at follow-up. Psychopathology (SCL-90-R): At baseline ayahuasca users scored significantly lower than controls across all nine SCL-90-R symptom dimensions and related indices, indicating fewer self-reported symptoms. At the one-year follow-up users again showed lower scores on most dimensions (reported as seven of nine), so many of the baseline differences persisted despite attrition. Neuropsychological performance and frontal behaviour (Stroop, WCST, LNS, FrSBe): On the Stroop test users performed better in the first assessment, with higher total words [F(1,235)=21.00; p<0.001] and total colours [F(1,235)=29.38; p<0.001], and superior performance on incongruent items. WCST results showed significantly fewer total errors in users at baseline (summary statistic reported but detailed figures not available in the extracted text). Working memory measured by LNS was higher in users at baseline [F(1,237)=21.27; p<0.001], with a larger effect in the Urban sample as indicated by a Group×Sample interaction [F(1,241)=5.86; p=0.016]; the overall group effect on LNS remained at follow-up [F(1,132)=5.52; p=0.020] though the interaction did not. The FrSBe global score was lower (better) in users at baseline [F(1,216)=31.81; p<0.001], and lower subscale scores were also reported. Life attitudes and well-being (SOI, PLT, BIEPS): Ayahuasca users scored higher on all nine components of the SOI at both assessments, aligning with elevated Self-Transcendence on the TCI. Users had higher Purpose in Life scores at baseline [F(1,216)=14.10; p<0.001], but this difference did not replicate at follow-up. Global psychosocial well-being (BIEPS) was higher in users at baseline [F(1,213)=16.17; p value not fully reported] and the group effect on the global BIEPS score remained at follow-up [F(1,115)=6.33; p=0.013]; Psychosocial Bonds also remained higher [F(1,115)=4.10; p=0.045]. A Group×Sample interaction for Projects [F(1,19)=4.75; p<0.05] indicated lower Project scores for urban users compared with urban controls. Adverse events and other findings: The extracted text did not report systematic clinical adverse events or diagnostic interviews indicating elevated psychiatric disorder prevalence among users. The investigators noted potential social desirability bias on self-report measures but reported PST subscale values that argued against extreme bias. Overall, baseline advantages for the ayahuasca group in psychopathology, cognition and spirituality were largely maintained at one-year follow-up, though sample attrition reduced power for some comparisons.

Bouso and colleagues interpret their findings as providing no evidence that long-term ritual ayahuasca use is associated with increased psychopathology, personality pathology or neuropsychological impairment. They highlight a personality profile in users characterised by lower Harm Avoidance and higher Reward Dependence and Self-Transcendence, together with lower Self-Directedness; the authors suggest these traits may partly reflect adaptation to community life in a challenging environment or be influenced by sustained ritual practice and doctrinal adherence. The elevated Self-Transcendence and consistently higher scores on the Spiritual Orientation Inventory are positioned as cohering with the religious context of ayahuasca use. With respect to mental health, the persistent pattern of lower SCL-90-R scores in users is discussed in two ways: either ritual ayahuasca use carries low risk for long-term psychopathology, or the observed pattern reflects self-selection, where individuals who tolerate the practice remain as long-term members. The authors note that lower symptom scores were still observed at follow-up, but they acknowledge that assessing ex-users would be important to evaluate discontinuation due to adverse effects. Regarding cognition, the study did not support hypotheses of frontal impairment related to 5-HT2A receptor activation; instead, users performed as well as or better than controls on measures of selective attention, executive function and working memory. The investigators consider possible explanations including preserved or enhanced cognitive functioning in these ritual users, animal data suggesting 5-HT2A involvement in cognition, and non-specific factors such as greater motivation among users during testing. Key limitations acknowledged by the authors include lack of matching for premorbid IQ, which complicates causal interpretation of cognitive differences; potential type I error from multiple comparisons given the comprehensive test battery; reliance on self-report instruments susceptible to social desirability bias; and self-selection bias whereby individuals experiencing adverse effects may have discontinued use and thus were not captured. The authors recommend future research include ex-users and control for premorbid cognitive ability to disentangle pre-existing differences from effects of ayahuasca. Overall, the authors conclude that, within the constraints and caveats they describe, long-term ritual ayahuasca use in these samples was not associated with psychological maladjustment or cognitive impairment and was accompanied by higher spirituality and psychosocial well-being.

The investigators conclude that their multi-domain assessment found no evidence of pathological alterations associated with long-term ritual ayahuasca use. Although users differed from controls on several personality dimensions, these did not constitute a pathological profile. Ayahuasca users reported fewer psychopathological symptoms, performed at least as well and in some measures better on neuropsychological tests, and scored higher on spirituality and certain psychosocial well-being indices. Many of these differences persisted at the one-year follow-up, but the authors reiterate limitations—particularly potential self-selection and lack of premorbid IQ matching—that temper causal inference and warrant further study.