Participation in an indigenous Amazonian led ayahuasca retreat associated with increases in nature relatedness - a pilot study
This preprint (n=58) assessed the association between participation in an ayahuasca retreat in a traditional indigenous Amazonian context and how it is related to nature-relatedness. Retreat participation was associated with increases in nature-relatedness, mindfulness and improvements in depression and anxiety.
Authors
- Gandy, S.
- Hollingdale, J.
- Netzband, N.
Published
Abstract
Indigenous Amazonian shamanic ayahuasca practice is deeply rooted in nature and it is employed as an ecological mediating agent and in collective environmental decision-making processes by some of the groups that use it. Phenomenologically, the ayahuasca experience is often rich in nature-based themes and content, and its usage has been associated with eliciting shifts in perspectives and attitudes towards nature. In this proof of concept study, participation in an ayahuasca retreat in a traditional indigenous Amazonian context (with a mean of 5.85 ceremonies attended) was associated with significant increases in nature relatedness (n = 24; Cohen’s d = .51) and mindfulness (n = 38; Cohen’s d = .75), and improvements in depression (n = 47; Cohen’s d = 1.18), state anxiety (n = 47; Cohen’s d = 1.02), and trait anxiety (n = 42; Cohen’s d = .88). Furthermore, significant negative correlations were found between changes in nature relatedness and depression (r = .623, p = .001), state anxiety (r = -.542, p = .008), and trait anxiety (r = -.485, p = .022), with a significant positive correlation between change in nature relatedness and mindfulness (r = .747, p = .001). It is currently unclear if the changes seen were due to consumption of the brew, participation in ceremony, or the retreat setting itself. Although this pilot study suggests a potential therapeutic role for Amazonian ayahuasca retreats as a multidimensional intervention, further work is required to assess the role of possible mediators underlying such shifts, while evaluating to what extent these are sustained long-term.
Research Summary of 'Participation in an indigenous Amazonian led ayahuasca retreat associated with increases in nature relatedness - a pilot study'
Introduction
Human psychological disconnection from the natural world has been linked to environmental degradation and poorer mental health, yet scalable interventions to restore this connection are limited. Ayahuasca, a traditional Amazonian psychedelic brew containing DMT and beta-carboline MAOIs, is commonly used in shamanic contexts that emphasise human–nature interconnection. Previous work has reported that psychedelic and specifically ayahuasca experiences often contain pronounced nature-based phenomenology, and that higher nature relatedness (a trait reflecting self-identification with and appreciation of the natural world) is associated with better wellbeing and pro-environmental attitudes. This pilot study set out to prospectively assess whether participation in indigenous Amazonian shaman‑led ayahuasca retreats in the Peruvian Amazon is associated with changes in nature relatedness. Ruffell and colleagues also evaluated whether concurrent changes in mystical experience, mindfulness, depression, and state and trait anxiety were associated with shifts in nature relatedness. Based on prior literature, the investigators hypothesised that retreat participation would increase nature relatedness.
Methods
The study used an observational, naturalistic design at the Ayahuasca Foundation (AF), a retreat centre located in the Allpahuayo‑Mishana National Reserve near Iquitos, Peru. Participants were a self-selected sample who travelled to the centre across eight separate retreats of varying lengths (8, 14, 18 and 28 days). A total of 58 participants enrolled after passing the centre's eligibility screening; medical diagnoses were self‑reported and not verified from records. The AF made inclusion decisions independently of the research team. Ethical approval was obtained and the study followed the Declaration of Helsinki. Retreat preparation required a two‑week ‘‘washout’’ from drugs and certain foods to reduce tyramine-related risks with MAOIs. Ceremonies followed an adapted Shipibo format: participants could attend between four and eleven voluntary ayahuasca ceremonies (typically 150–200 ml per serving, dosing left to curandero and participant discretion), each lasting around six hours at night in a communal maloka with one shaman and Western facilitators. Participants completed baseline measures before their first ceremony (at a hotel in Iquitos) and post‑retreat measures the morning after their final ceremony (at the AF). Psychological measures included the six‑item Short Form Nature Relatedness Scale (NR‑6), Beck Depression Inventory II (BDI‑II), State‑Trait Anxiety Inventory (STAI state and trait), Five Facet Mindfulness Questionnaire (FFMQ) and the 30‑item Mystical Experience Questionnaire (MEQ). Reliability analyses reported acceptable to strong internal consistency for these instruments in the sample. The MEQ was administered only at the post‑retreat time point and was used to capture experience across the entire retreat rather than individual sessions. Statistical analyses were conducted in SPSS 27.0. Paired two‑tailed t‑tests compared pre‑ and post‑retreat means and Cohen's d was reported as the effect size measure (with d > .80 considered large). The Holm‑Bonferroni procedure corrected for multiple comparisons. Pearson bivariate correlations assessed relationships among change scores, with an exploratory alpha set at .01. Data screening included Shapiro–Wilk tests for normality and removal of identified outliers; the authors report removal of four outliers from correlation analyses. There was substantial missing data across measures (for example, 24/58 completed the NR‑6 and 47/58 completed the BDI‑II pre/post), which reduced sample sizes for some analyses.
Results
Participation in the indigenous Amazonian ayahuasca retreats was associated with statistically significant pre‑to‑post improvements across the measured domains, with medium to large reported effect sizes. Missingness varied by measure: 47 participants completed pre/post BDI‑II and STAI‑state, 42 completed STAI‑trait, 38 completed the FFMQ, 24 completed the NR‑6, and 50 completed the MEQ at the post‑retreat assessment. For nature relatedness specifically, mean NR‑6 scores increased from a reported baseline of 4.10/5 to 4.36/5 after the retreat. Primary correlation analyses showed statistically significant negative associations between change in NR‑6 and changes in depression (BDI‑II) and both state and trait anxiety (STAI), indicating that increases in nature relatedness were associated with reductions in these clinical symptoms. Change in NR‑6 was also significantly positively correlated with change in mindfulness as measured by the FFMQ. The MEQ change (measured only post‑retreat as the overall retreat score) was not significantly correlated with pre‑post change scores on nature relatedness, mindfulness, depression or anxiety. Despite the lack of correlation, 34 of 42 participants who completed the MEQ (81%) met the study's threshold for a ‘‘complete mystical experience’’ (≥ 60% on each MEQ subscale). No relationships were found between age, gender, or prior lifetime ayahuasca/psychedelic use and the primary outcomes. The number of ceremonies attended did not correlate with changes in nature relatedness, while there was a trend towards an association between longer total retreat duration (days at the centre) and greater increases in nature relatedness. Four outliers were removed from correlation analyses as noted, and the Holm‑Bonferroni correction was applied to control familywise error.
Discussion
Ruffell and colleagues interpret the findings as preliminary evidence that participating in indigenous Amazonian ayahuasca retreats is associated with increased nature relatedness alongside reductions in depression and anxiety and increases in mindfulness. The reported negative correlations between increases in nature relatedness and reductions in depression and both state and trait anxiety, together with the positive correlation between nature relatedness and mindfulness, led the investigators to propose that enhanced connection to nature may be a clinically relevant pathway linked to mental health benefits observed after retreat participation. The authors position these results within prior research that has linked psychedelics and ayahuasca to shifts in nature‑related attitudes and pro‑environmental behaviour, noting that post‑retreat NR‑6 scores in this sample were higher than typical community baselines reported in other studies. They emphasise the likely influence of contextual factors: traditional shamanic framing, immersion in a biodiverse rainforest setting, enforced disconnection from technology, and time spent at the retreat may mediate increases in nature relatedness independently of or in addition to the pharmacological effects of ayahuasca. The lack of correlation between MEQ scores and outcome changes is discussed in light of methodological issues — notably that the MEQ was used to assess the whole retreat rather than individual sessions — and compared with other studies where mystical experience has predicted clinical outcomes. The authors acknowledge multiple important limitations. This was an uncontrolled, naturalistic pilot with substantial missing data and attrition, limiting statistical power and precluding long‑term follow‑up. The self‑selected, predominantly Western and higher‑income sample reduces generalisability and may be biased by higher baseline openness to experience; ceiling effects are possible because baseline nature relatedness was already high. Measures were collected in different physical settings pre‑ and post‑retreat (hotel versus rainforest centre), which could have influenced responses. The investigators were unable to analyse the chemical constituents of the ayahuasca brew, so dose and alkaloid composition could not be related to outcomes. Given these limitations, the authors call for larger, controlled studies, longer follow‑up, and investigation of mediators and mechanisms; they outline plans for a ‘‘placebo’’ retreat control condition that would mimic the retreat context without serving ayahuasca to help disentangle contextual versus pharmacological effects. Finally, the paper discusses practical implications raised by the authors: simple adjunctive practices such as nature journaling, mindful walking, Shinrin‑Yoku (forest bathing), and mindfulness training may amplify and help sustain increases in nature relatedness after psychedelic retreat participation. The investigators suggest that enhancing nature relatedness could be an additional therapeutic target when administering psychedelics, with potential benefits for both mental health and pro‑environmental attitudes.
Conclusion
The pilot study tentatively suggests that ceremonial ayahuasca retreats in an indigenous Amazonian setting may increase individuals' psychological connection to nature and coincide with improvements in depression, anxiety, and mindfulness, while recognising substantial methodological caveats. Ruffell and colleagues recommend further research to determine the durability of these changes, to identify the specific factors mediating the shift in nature relatedness, and to assess how such effects might be augmented, given the potential relevance for human and planetary health.
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INTRODUCTION
A growing human psychological disconnection from the natural world has been linked to environmental destruction and negative impacts on mental health. In spite of the utmost urgency warranted in reversing this, there is a lack of interventions which can effectively reconnect individuals to the natural world. Ayahuasca is a psychedelic plantderived decoction containing beta-carboline MAOI alkaloids and the psychedelic compound DMT with a long-history of shamanic usage in Amazonia. Ayahuasca experiences often feature a strong phenomenological component of nature, with nature-based content and themes commonly described, including experiences of interconnection with nature. Traditional Amazonian shamanic ayahuasca practice is deeply rooted in nature, with shamanic rituals and teachings often emphasising the shared interconnection of humans with nature, with this also applying to Europeanand Australianneoshamanic contexts. Ayahuasca plays a prominent role as an ecological mediating agent among some Amazonian indigenous groups that use it, as a bridge between humans and non-human life and the wider forest landscapes, and it can play a role in collective environmental decision-making processes. Nature relatedness (sometimes referred to as nature connectedness in the literature) is a measure of one's self identification with nature, encompassing "one's appreciation for and understanding of our interconnectedness with all other living things on the earth", and it is tied to a sense of kinship with the wider natural world as part of a larger community of nature. It has been linked to better overall mental and physical healthand strongly associated with eudaimonic well-being (for a review, see, far exceeding the association between the latter and socioeconomic status in one study. It is also associated with greater contact with nature, while being an important mediator for some of the benefits to mood and cognition yielded by the latter (for a review, seeand it is a key predictor of pro-nature attitudes and behaviours. Nature relatedness appears to be a deeply held and stable trait, and resistant to change like other environmental attitudes. Human connection to nature is being increasingly eroded, partly through increasing urbanisationand a loss of green space, meaning increasing numbers of people are inhabiting nature-depleted environments. This can result in a diminished potential for everyday interactions with nature or an 'extinction of experience', and this reduced capacity for nature contact and connection has detrimental implications for health, wellbeing, and propensity towards experiencing positive emotions. While there are a range of nature relatedness enhancing interventions, including nature immersion retreats, nature-based educational programmes, and nature-based engagement programmes, these may be time and resource heavy and variable in their effectiveness, with a need for reliable and robust interventions. Psychedelic mystical experiences have been associated with states of interconnectednessand frequently correlated with positive changes in people's relationship with nature. In addition, mystical experiences have been identified as a factor contributing to reductions in depression and anxiety associated with ayahuasca usage. This formed the rationale for assessing the degree to which mystical experiences were correlated with shifts in nature relatedness and associated with changes in depression and anxiety. Ayahuasca has also been associated with enhancing mindfulness, which shares a positive reciprocal relationship with nature relatedness. Nature relatedness has been associated with lower levels of state and trait anxiety, of mental distress and antidepressant medication prescription usage, and positively associated with psychological resilience. However, aspects of nature relatedness tied to self-identification with nature and a concern for conserving nature have been linked to increased depression, anxiety, and stress, possibly due to an increased awareness of human driven ecological destruction. This paper assesses whether participation in Amazonian ayahuasca retreats, as a multidimensional intervention, results in change in nature relatedness. Furthermore, this study evaluates whether changes in mystical experience, mindfulness, depression, trait, and state anxiety are associated with shifts in nature relatedness. While previous studies have highlighted an association between experience with classical psychedelics and nature relatedness, this is the first study to prospectively assess the effect of participation in an indigenous Amazonian shaman led ayahuasca retreat in the Peruvian Amazon on nature relatedness. Inferring from previous research, it is expected that participation in an ayahuasca retreat will likely enhance levels of nature relatedness.
SETTING
Data was collected at the Ayahuasca Foundation (AF). This ayahuasca retreat centre is situated three hours from the nearest city, Iquitos, in the Peruvian Amazon. The self-selected sample were required to travel by car and then by boat to reach the centre. The retreat and research centre is located in the Allpahuayo-Mishana National Reserve. The Mishana community is 20 miles from Iquitos, has no mains electricity and is almost completely free from phone signal and internet access. Participants 58 participants were enrolled in total after meeting the retreat centre's eligibility criteria. The information provided was self-reported and diagnoses were not confirmed with medical records by the researchers (see Tablefor participant demographics). Participants were asked to report their lifetime use of substances, defined as use of a substance on at least one occasion during their lifetime. 11 (18.96%) reported previous use of ayahuasca, ranging between 1-42 times (see Tablefor lifetime use of substances amongst participants). Data was collected from participants across eight jungle retreats. Number of participants per retreat length were 34 (58.62%) in the 8-day, 6 (10.34%) in the 14-day, 6 (10.34%) in the 18-day, and 12 (20.69%) in the 28-day retreat. All data from varying retreat lengths were included in the analyses, with subsequent analyses conducted to determine the effect of differing retreat duration as well as the number of ceremonies attended on outcomes., as well as moderate-to-high correlations between pre-post change scores (rs = .53-.55;. Although we did not perform a formal a priori power analysis, the sample size of 58 participants provides 80% power to detect weak effects (d > .37, r > .35), assuming two-tailed alpha = .05 (G* Power 3.1;, which suggests that the present sample was sufficient to detect effects similar to, and much smaller than, those reported in previous studies. Unfortunately, there was significant missing data on several measures, however, even when accounting for the reduced sample size, a sample of 24 participants provides 80% power to detect moderate effects (d > .59, r > .51), assuming two-tailed alpha = .05, which indicates that even the analyses performed on the data with the smallest sample size were sufficiently powered to detect effects similar to those reported in previous studies.
DESIGN
This study followed an observational, naturalistic design. Participants attending the retreats were informed of the research by the AF two weeks before arriving at the centre. Retreat facilitators provided potential research participants with information sheets outlining the research upon arrival in Iquitos. Participation was voluntary and participants were able to withdraw consent at any time. The AF collected information from participants before they were accepted onto retreats. Online forms were utilised, with questions surrounding medications and physical and mental health conditions. Participants were forbidden from attending retreats if they disclosed personality disorders or conditions that were psychotic in nature (schizophrenia, bipolar disorder etc). The decision to include participants on the retreats was made solely by the AF and independently of the research team. Ethical approval was acquired (#CLESPsy000893 v2.0) and the study is in concordance with the declaration of Helsinki.
RETREAT PREPARATION
Participants were required to adhere to a "washout period" before attending retreat. For the two weeks prior to retreat commencement, abstinence from drugs (both prescription and recreational), fatty food, salt, red meat and sugar was required. Dietary restrictions were largely to lower levels of tyramine, which, when combined with MAOIs has the potential to result in nausea, cardiovascular overactivity, and headaches.
MEASURES SHORT FORM NATURE RELATEDNESS SCALE
For the sake of parsimony, a validated six-item measure, the Short form Nature Relatedness Scale (NR-6) scalewas used to assess people's subjective sense of self-identification with nature, or their connectedness to it, this being a short form version of the larger Nature Relatedness (NR) scale. Participants rated the degree to which they agreed with six statements on a 5-point Likert scale (1 = 'disagree strongly' to 5 = 'agree strongly'). The six items were: 'My ideal vacation spot would be a remote, wilderness area'; 'I always think about how my actions affect the environment'; 'My connection to nature and the environment is a part of my spirituality'; 'I take notice of wildlife wherever I am'; 'My relationship to nature is an important part of who I am' and 'I feel connected to all living things and the earth'. The mean of the answers across the six items was used as a measure of nature relatedness, with higher scores corresponding to higher ratings of nature relatedness. The NR-6 has been shown to demonstrate temporal stability, with high onemonth test-retest reliability (r = .93), as well as predicting happiness and environmental outcomes similarly to the full scale. A reliability analysis carried out on the NR-6 for internal consistency indicated that it reached acceptable reliability in our sample (Cronbach's alpha = .80). Unfortunately, there was a significant amount of missing data associated with this scale. Missing NR-6 responses were likely due to unclear formatting when completing the electronic battery, in which participants were required to scroll further after previous questions. Of the total sample of 58 participants, 24 successfully completed the NR-6 scale with 34 leaving the questionnaire incomplete. This has now been addressed for follow up studies.
BECK DEPRESSION INVENTORY-SECOND EDITION
The Beck Depression Inventory-Second Edition (BDI-II) is one of the most frequently used self-report measures of depression severity. This 21-item scale assesses the psychological symptoms of depression such as irritability and hopelessness, cognitions including guilt or feelings of being punished as well as physical symptomatology including shifts in sexual desire, weight loss and fatigue. Each question is scored on a four-point Likert scale ranging from zero to three. Higher scores suggest more severe depression, with scores between 0-13 indicative of minimal depression, 14-19 mild depression, 20-28 moderate depression and 29-63 severe depression. The BDI-II has been demonstrated to be valid, with high one-week test-retest reliability (r = .93), demonstrating a lack of sensitivity to daily mood fluctuations. A reliability analysis carried out on the BDI-II for internal consistency indicated that it displayed strong reliability in our sample (Cronbach's alpha = .95).
STATE-TRAIT ANXIETY INVENTORY
The range from 20 to 80, with higher levels of anxiety correlating with higher scores on the inventory. The STAI has been found to demonstrate both construct and concurrent validity.found test-retest reliability coefficients ranging between .65 and .75 over a two-month period. A reliability analysis indicated that the STAI state anxiety items exhibited strong reliability in our sample (Cronbach's alpha = .95), as did the trait anxiety items (Cronbach's alpha = .95).
MYSTICAL EXPERIENCE QUESTIONNAIRE
The Mystical Experience Questionnaire (MEQ) comprises 30 items and measures peak experiences. This validated tool assesses four factors; Transcendence of Time and Space (a sense of being outside of the past and the future), Positive Mood (feelings of tranquillity and peace), Ineffability (incapability to describe the experience in words) and Mystical Experience (items pertaining to both internal and external unity as well as possessing a noetic quality;. Participants are required to rate the intensity with which they experienced each of the items on a six-point scale ranging from 0= 'not at all; none' to 5= 'more than ever before in my life and stronger than 4; extreme'. Participants were considered to have undergone a 'complete mystical experience' when ≥ 60% of the maximum possible score on each subscale was endorsed. The MEQ has been shown to demonstrate sensitivity when assessing the effects of ayahuasca in previous research. A reliability analysis carried out on the MEQ indicated that it reached acceptable reliability in our sample (Cronbach's alpha = .97). Data was only collected using this tool at time point two to evaluate the effect of the retreat. As such, ratings reflected the entire retreat, rather than single ceremonies.
FIVE FACETS MINDFULNESS QUESTIONNAIRE
The Five Facets Mindfulness Questionnaire (FFMQ) is a self-report measure comprised of 39 items assessing the five facets; Acting with awareness, Observing, Describing, Nonreactivity and Nonjudging. Acting with awareness describes one's ability to attend to the present moment. Observing refers to the ability to notice experiences, both internal and external, for example emotions and bodily sensations. Describing involves putting experiences into words. Nonreactivity is the ability to refrain from one's involvement in thoughts and emotions, allowing them to pass freely. Finally, Nonjudging involves refraining from the evaluation of thoughts and emotions. Each of the items are measured on a 5-point Likert-type Scale (1 = 'very rarely true', 5 = 'very often true'), for example 'I pay attention to physical experiences such as the wind in my hair or the sun on my face'. Scores for each facet range between 8-40, other than Nonreactivity, which ranges between 7-35. Scores can be used for the five subscales individually or combined to form an overall mindfulness score, with higher scores representing a greater degree of mindfulness. The FFMQ has been demonstrated to show both discriminant and convergent validity as well as adequate internal reliability in both clinical and non-clinical samples.found test-retest reliability coefficients of the FFMQ facets ranging between .61 (acting with awareness) to .84 (nonjudging). A reliability analysis carried out on the FFMQ indicated that it reached acceptable reliability in our sample (Cronbach's alpha = .95).
PROCEDURE
The AF administers ayahuasca in an adapted traditional Shipibo format. Retreat length varies, from eight days to one month. Participants were offered either four, six, nine, or eleven ayahuasca ceremonies, although participation was voluntary. The exact number of ceremonies attended was recorded. Ayahuasca ceremonies lasted for around six hours and took place at night. Two to three Western facilitators assisted a shaman (curandero) throughout the rituals. Ceremonies took place in the 'maloka', a circular wooden structure, with participants sitting around the edge. Each participant was provided with a bucket for 'the purge' -vomiting that is typically associated with the brew. Participants were evenly spaced on individual mattresses and instructed to avoid contact with one another throughout the ceremony. Ayahuasca was consumed at around 20:00 after intentions for the ceremony had been set. Following this the curandero sang 'icaros' (traditional medicine songs), with facilitators helping participants if required. The dose of ayahuasca was left to the curandero and the participants discretion (usually 150-200ml). Participants completed inventories before their first ceremony and the morning after their final ceremony. Pre-retreat data collection took place at a hotel in Iquitos, and post-retreat data collection at the AF in the Mishana community. Laptop computers were provided in each instance.
DATA ANALYSIS
Data is analysed using SPSS 27.0. Paired-samples two-tailed t-tests were used to compare mean differences across time and only total scores were used in the present analysis. The multistage effect sizes were calculated using Cohen's d and were considered large when .80 (d > .80)). The Holm-Bonferroni procedure was applied to analyses to correct for multiple comparisons. It should be noted that there were a large number of missing datasets in this study. 47 of the 58 enrolled participants completed the BDI-II pre and post retreat, 47 completed the STAI-S, 42 the STAI-T, 38 the FFMQ, 24 the NR-6 and 50 the MEQ at time point two. Pearson's bivariate correlation analyses were used to compute r values. Correlation coefficients ranging between .30 and .70 were deemed moderate. Explorative correlation analyses were conducted with an alpha level set at .01 to control for multiple comparisons. All data were normally distributed (Shapiro-Wilk test), and outliers were assessed for using boxplots and scatterplots. Four outliers were removed from the correlation analyses, one from the primary analysis and three from the exploratory analyses, after being identified on scatterplots and have been reported in the results.
PRE AND POST AYAHUASCA RETREAT OUTCOMES
Our first set of analyses examined whether participation in Amazonian ayahuasca retreats was associated with changes in the different research measures utilised (see Tablefor descriptive and inferential statistics). Paired samples t-tests showed that participation in Amazonian ayahuasca retreats was associated with significant improvements on all measures, with medium to large effect sizes. This suggests that participation in such retreats as a multidimensional intervention could evoke significant changes in a variety of domains.
PRIMARY CORRELATION ANALYSIS OF CHANGE SCORES
A priori analyses involved correlating the NR-6 with the BDI-II, STAI-S, and STAI-T. One outlier was removed from the NR-6 and STAI-S correlation and the remaining assumptions for correlations were met. A statistically significant negative correlation with moderate effect size was found between NR-6 change scores and BDI-II, STAI-S, and STAI-T change scores (see Tablefor primary correlation analyses). This suggests that changes in nature relatedness is associated with decreased scores on clinical outcome measures after attending Amazonian ayahuasca retreats in our sample.
TABLE 4
Primary .01 to control for multiple comparisons. One outlier was removed from the BDI-II and STAI-T correlation, one from the FFMQ and STAI-T correlation, and one from the FFMQ and NR-6 correlation, and all remaining assumptions were met. A statistically significant positive correlation with a large effect size was found between the NR-6 and FFMQ change scores (see Tablefor correlation matrix of pre-post change scores). The MEQ was not found to significantly correlate with any of the change scores in research measures, despite 34 of the 42 participants (81.0%) who answered the MEQ qualifying for a "complete mystical experience", defined as a score of 60% or more on each of the four subscales.
DISCUSSION
Participation in Amazonian ayahuasca retreats in a traditional indigenous context (with a mean attendance of 5.85 ceremonies) was associated with reductions in depression, state, and trait anxiety, and increases in mindfulness and nature relatedness. Increases in nature relatedness were found to be negatively correlated with depression, state, and trait anxiety, and positively correlated with mindfulness scores. Thus, this multidimensional intervention identified positive changes. However, the mechanisms of change, including the contributions of each component to effect change, need to be explored further. No relationship was found between age, gender, and history of past ayahuasca or psychedelic usage.
AYAHUASCA AND NATURE RELATEDNESS
The finding that participation in Amazonian ayahuasca retreats was associated with a significant increase in nature relatedness builds on previous research reporting links between ayahuasca usage and shifts in individuals' relationships with nature (see Table). The mean baseline nature relatedness of participants in this study was high (4.10/5), with a mean nature relatedness of 4.36 post ayahuasca retreat participation, with a number of pooled studies reporting that mean baseline scores ranged from 3.00-3.44 in Canadian student and community populations sampled. Mean levels of nature relatedness following ayahuasca retreat participation exceed median nature relatedness levels reported in one study (4.2) with a sample of individuals reporting a broad range of lifetime psychedelic usageand were similar to mean levels of nature relatedness (4.45) in one study sample comprising individuals reporting over 100 psychedelic experiences. It is important to acknowledge the possible influence of contextual factors in this study. Traditional, indigenous shaman led ayahuasca ceremonies have an inclination towards nature-based content and themesand likely act as a mediating influence that affects people's relationship with nature, aside from the direct pharmacodynamic effects of ayahuasca itself. It is noteworthy that while no correlation was found between the number of ayahuasca ceremonies individuals participated in and shifts in nature relatedness, there was a trend towards significance when comparing number of days spent at the retreat centre and changes in nature relatedness, suggesting the rainforest setting may have influenced individuals' nature relatedness above and beyond ayahuasca ceremonies alone. Contact with biodiverse or nature-rich environments may promote greater nature relatedness, and nature-based experiences or interventions of greater time duration are more likely to elicit increases in nature relatedness. Furthermore, given limited electricity and a lack of phone signal or internet access at the retreat centre, retreat participants would have been forced to disconnect from technology for the duration of their time there. This may have facilitated greater connection to nature while attending the retreat, with usage of electronic entertainment technology and smartphones negatively associated with nature relatedness. Ayahuasca commonly changes the way users perceive their relationship with nature during and after the experienceand healing relationships with nature is a commonly reported beneficial outcome of ayahuasca usage. People report a greater interconnection with nature, greater sensitivity towards it, and a proclivity to spend more time in nature with feelings of safety and confidence following ayahuasca usage. Ayahuasca usage has also been associated with generating more respectful relationships with nature, inspiring nature-orientated interestsand in generating pro-environmental awareness and attitudes. Such shifts are likely mediated in part through an increase in nature relatedness. While this study did not assess long-term changes in nature relatedness, inferring from previous research, such shifts are likely to be enduring. Positive changes to people's relationship with nature and their connection to it following a psychedelic experience has been found to be sustained for at least 1-2 years according to past research and increased nature relatedness and a deepened appreciation of nature can occur after 1-2 psychedelic sessions. Further research could assess to what degree increases in nature relatedness elicited by Amazonian ayahuasca retreat participation are sustained long-term.
NATURE RELATEDNESS INCREASE CORRELATING WITH REDUCTIONS IN DEPRESSION AND ANXIETY
The occurrence of mystical experiences assessed via the MEQ was not correlated with changes in nature relatedness, mindfulness or depression and anxiety scores, while nature relatedness was found to be significantly negatively correlated with depression, trait, and state anxiety, and positively correlated with mindfulness scores. Other research has found nature relatedness to be more consistently associated with measures assessing happiness, positive affect, and personal growth than depression and negative affect, particularly after controlling for general connectedness. The only other published prospective study that has examined a potential link between changes in nature relatedness elicited by psychedelic administration and depression found no correlation, but this study was limited by a small sample size (n=7). The lack of evidence demonstrating a link between the occurrence of mystical experiences and changes in clinical outcomes is noteworthy, being in contrast to other studies where the occurrence and intensity of mystical experiences was found to be a significant factor predicting improvements in depression and anxiety. However, one randomised placebo-controlled trial evaluating the antidepressant potential of ayahuasca found that only one factor of the MEQ (transcendence of time and space) showed a significant association with a reduction in depression scores, whereas the other three factors (ineffability, mystical and positive mood) did not. In our sample, 81.0% of participants qualified for a "complete mystical experience", scoring 60% or more in each of the four core dimensions of the MEQ. This is a large proportion of subjects when compared to other psychedelic research, exceeding that reported in early work conducted by Pahnke, which reported complete mystical experiences in 30-40% of participants, and in a range of naturalistic survey studies (seeand in a more recent study where 61.1% of participants qualified for a complete mystical experience following psilocybin administration. Higher ratings of complete mystical experiences have been reported with psilocybin administered in a mindfulness meditation retreat context among Zen Buddhist meditation practitioners, with 95% reporting such experiences, and in association with usage of 5-MeO-DMT in a supportive context, with such experiences reported among 75%and 83%of participants in the latter studies. The high scores on the MEQ in our sample may result from the non-standard use of the scale to measure the entire retreat, rather than for a single psychedelic session as it was designed. This methodological limitation may account for the lack of relationship between MEQ scores and anxiety and depression, which is well established in the literature (for a review, see. While no association was found between the number of ceremonies attended and nature relatedness, there was a trend association between retreat duration and nature relatedness. This could indicate that the retreat environment itself may have a greater impact on nature relatedness than attending ayahuasca ceremonies and the mystical experiences associated with ceremonial ayahuasca consumption. Further research with larger sample sizes is however required to explore this before any conclusions can be drawn. While other studies have identified factors such as psychological insight, personal meaning and emotional breakthrough experiences as being important determinants of clinical response associated with psychedelics, this is the first study to suggest that nature relatedness increase associated with the psychedelic experience may also have clinical relevance. While the potential implications of enhancing nature relatedness through psychedelic administration has largely been overlooked until recent times, it has been argued that maximising enhancement of nature relatedness when administering psychedelics may constitute an important supplemental pathway to improved mental health outcomes. Participation in Amazonian ayahuasca retreats in the present study was associated with increased mindfulness and change in nature relatedness scores were found to positively correlate with mindfulness as assessed via the FFMQ (see Tablesand). Previous studies have found ayahuasca usage to be associated with higher levels of an aspect of mindfulness referred to as decentering. Decentering involves a non-judgmental and accepting perspective of inner psychological content, having been defined as "the realization that thoughts, feelings, and reactions are transitory patterns of mental activity, that they are not necessarily true representations of the self and events". Nature relatedness was found to have a borderline significant negative association with rumination (a propensity to dwell on negative thoughts or the symptoms of one's distress) in one study, and there is a strong association between rumination and depression and anxiety disorders (for reviews, see. Rumination and decentering can be considered as opposing and inversely correlated psychological processes, and decentering has been associated with mediating reductions in anxiety and depression, while also mediating the relationship between trait or dispositional mindfulness and nature relatedness. Increases in nature relatedness and associated decreases in depression and anxiety following Amazonian ayahuasca retreat participation may partly occur through a decentering-mediated disidentification with internal psychological content which may in turn liberate mental resources to allow contextual awareness to expand, so increasing receptivity to the external, natural world.
STUDY LIMITATIONS AND FUTURE RESEARCH
This was a proof-of-concept study with no control group. There was a significant attrition rate, which prevented long-term follow up, and a future study protocol has been amended in order to mitigate this to help ensure collection of long-term data. It should be noted that this study was underpowered due to a large number of missing data points and results regarding nature relatedness should be interpreted with caution. Further, constituent analysis of the brew was not possible for logistical reasons, preventing us from comparing outcomes to the levels of DMT and harmala alkaloids ingested. Generalisability of findings are limited due to the self-selected nature of the sample and participants being mainly Western and of higher income status. Further research should seek to assess a broader demographic of individuals. Positive sample bias may be a factor in this population, in that people attending a retreat with the intention of ingesting a psychedelic such as ayahuasca may have a greater than average openness towards new experiences. Personality trait openness is one of the primary personality correlates of nature relatedness. There may be a ceiling effect issue when assessing change in connection to nature using short item scales when baseline measures are already high, as they were in this sample. While shorter item measures are convenient for research purposes, one potential way of mitigating this issue would be to use longer but psychometrically superior measures such as the Disposition to Connect with Nature scale. It A further methodological limitation is the lack of a consistent environment in which participants completed the inventories. Pre-retreat data collection took place at a hotel in Iquitos, whereas post-retreat data collection was completed at the AF in the Mishana community. The differences in location of nature relatedness sampling may have influenced participant's responses, leading to difficulties in determining the effect of the retreat opposed to the setting in which the questionnaire was completed. The setting in which inventories are completed will be standardised in future studies. Whilst our data suggest nature relatedness could be related to changes in mental health outcomes such as depression and anxiety, our modest, uncontrolled sample does not allow for the generalisation of results. Future studies with larger samples and long term follow up will shed more light on the initial findings presented in this pilot study. Control groups for studies investigating psychedelics in retreat settings have proved problematic, with various authors attempting to address this issue. As we continue to evaluate the effects of ayahuasca in Amazonian retreat settings we plan to run a "placebo" retreat. This will follow the same structure as a regular ayahuasca retreat, however during ceremonies no ayahuasca will be served. It is hoped this will go some way towards controlling some of the numerous confounding variables, such as the shamanicceremonial context, immersion in nature, use of other plant treatments, smoke and vapour baths, and disconnection from electronic technology and the Western world in general.
ENHANCING NATURE RELATEDNESS
The practice of journaling has been found to effectively supplement psychedelic sessions, enhancing the long-term psychological benefits obtained. Journaling about nature (recording three things one enjoys about nature each day for five days) has been found to increase nature relatedness in a robust and sustained way. Application of such a practice before and after an ayahuasca experience may supplement the enhancement of nature relatedness. Building on this study, another reported that mindful walking in natural settings for 30 minutes a day (noting things that were enjoyed) was associated with increased nature relatedness, well-being, and positive affect. This suggests that this simple and cost-effective practice could be a beneficial way for individuals to supplement increases in nature relatedness and these benefits to mental health following participation in ayahuasca ceremonies. Mindfulness practices have been found to synergise with psilocybin administration, enhancing the long-term psychological benefits reportedwhile also enhancing nature relatedness, so application of mindfulness practices may augment the psychological benefits of ayahuasca while synergising with increases in nature relatedness. Contact with nature-based settings can promote mindfulness, and mindfulness in turn can enhance the benefits of contact with such settings. The practice of Shinrin-Yoku (forest bathing), an active form of nature-based mindfulness practice) may be a beneficial exercise both prior to and post ayahuasca experiences, to help facilitate mindful and soothing contact with nature. Such practices may be particularly beneficial for people following ayahuasca experiences when integrating back into city life. For additional suggestions on how to incorporate more nature-based content, practices, and settings into psychedelic sessions, seeAyahuasca usage in a traditional shamanic context (in the same setting as the present study) has also been found to significantly reduce neuroticism, with changes sustained at 6month follow up. Lower neuroticism scores are associated with greater psychological benefits obtained through contact with nature. Ayahuasca usage could result in people adopting more beneficial nature-centric lifestyles, with nature contact heavily underutilised and undervalued as a health promoting intervention.
CONCLUSION
This pilot study tentatively suggests that participation in ceremonial ayahuasca retreats in the Amazon rainforest may increase individuals' psychological connection to nature and associated benefits for mental health and well-being, mindful of methodological limitations. Further research should seek to elucidate to what degree this shift in individuals' connection to nature is sustained, further explore the specific factors that mediate this shift, and how it might be enhanced. Given that a growing disconnection from nature is implicated with both environmentally damaging behaviour and poor psychological health, reversing this trend could help promote synergistic improvements in human and planetary health.