Lifetime experience with (classic) psychedelics predicts pro-environmental behavior through an increase in nature relatedness

The study used a cross-sectional survey design administered via Amazon Mechanical Turk. After exclusions for random or purposive incorrect responding, the final sample comprised 1,487 participants (913 female, 566 male, 8 other), mean age 35.77 years (SD = 11.88), age range 18–78. Participants received modest financial compensation. Participants completed a bespoke lifetime substance-use questionnaire covering 30 psychoactive substances; for each substance they first indicated ever-use (binary) and, if yes, rated frequency of past use on a 1 (very rarely) to 5 (very often) scale, with non-users scored as 0. The authors grouped substances into classes for analysis: classic psychedelics (5-HT2A agonists, e.g. LSD, psilocybin, mescaline, ibogaine), dissociative anesthetics, empathogens/entactogens (e.g. MDMA), natural deliriants and related compounds, cannabinoids, and popular legal drugs (caffeine, nicotine, alcohol). Nature relatedness was measured using Nisbet and colleagues’ 21-item Nature Relatedness Questionnaire, which yields three subscales: NR-Self (internal identification with nature), NR-Perspective (attitudes about humans’ impact and entitlement), and NR-Experience (affective attraction to nature). Self-reported pro-environmental behaviour was assessed with 17 items adapted from UK DEFRA ‘‘headline behaviours’’, rated on a 4-point frequency scale (never to always). Personality was measured with the Ten-Item Personality Inventory to capture Big Five traits; additional controls included demographics, socio-economic status, general attitude toward psychoactive substances, and political orientation (1 = strongly liberal to 7 = strongly conservative). A single binary item screened for random responding. Data analysis employed structural equation modelling using the lavaan package in R. To reduce estimation error, the three NR subscales’ items were parceled once and the 17 pro-environmental behaviour items were parceled twice. Full information maximum likelihood (FIML) estimation handled missing data. The primary model specified latent variables for substance-class lifetime experience predicting the three NR subscales and, in turn, pro-environmental behaviour, with personality and political orientation included as covariates. The authors report post-hoc model modifications driven by low prevalence (leading to removal of the natural deliriants latent variable) and by modification indices that justified adding covariances among several substance indicators. Mediation of the psychedelics → NR-Self → pro-environmental behaviour pathway was tested by adding a direct path from classic psychedelics to pro-environmental behaviour and assessing indirect effects.

Prevalence and model adjustments: 26.9% of participants reported lifetime experience with at least one classic psychedelic substance. The authors dropped the latent variable for natural deliriants because under 1% of the sample reported experience with those substances. Modification indices indicated meaningful covariation between some ‘‘other’’ substance indicators (e.g. other psychedelics with other dissociatives and other empathogens), which was added to improve model fit. Model fit and covariation: The structural equation model showed acceptable fit: CFI = .889, TLI = .869, RMSEA = .052 (90% CI = [.050; .054]). Lifetime experience with each substance class was highly intercorrelated (all p < .001). Personality covariates behaved as predicted: political conservatism and conscientiousness were negatively associated with substance experience (conservatism all p < .001; conscientiousness all p < .01), while openness to experience was positively associated (all p < .0001). The three NR subscales were strongly intercorrelated (NR-Experience with NR-Self β = 0.724; NR-Perspective with NR-Self β = 0.746; all p < .0000001). Key predictive paths: As hypothesised, lifetime experience with classic psychedelic substances uniquely predicted two NR subscales: NR-Self (β = 0.303, SE = 0.081, p < .001, 95% CI = [0.144; 0.462]) and NR-Experience (β = 0.256, SE = 0.087, p = .003, 95% CI = [0.086; 0.427]). The prediction of NR-Perspective by classic psychedelics was marginal (β = 0.150, SE = 0.087, p = .085). No other substance class significantly predicted the NR subscales in the primary model, though two marginal and unpredicted pathways (dissociatives negatively predicting NR-Perspective; popular legal drugs positively predicting NR-Experience) emerged but became non-significant when alternative covariates were included. NR-Self and pro-environmental behaviour: When accounting for intercorrelations among NR subscales, NR-Self alone significantly predicted self-reported pro-environmental behaviour (β = 0.638, SE = 0.086, p < .0000001, 95% CI = [0.470; 0.806]). The other two NR subscales did not predict these behaviours in the full model. In addition, conscientiousness directly predicted pro-environmental behaviour (β = 0.070, SE = 0.023, p = .002), and political conservatism had a small negative direct effect (β = -0.064, SE = 0.028, p = .025). Mediation and alternative models: Mediation analysis indicated a significant indirect effect of classic psychedelic experience on pro-environmental behaviour via NR-Self (indirect β = 0.182, SE = 0.056, p = .001, 95% CI = [0.073; 0.292]). The total effect of lifetime psychedelic experience on pro-environmental behaviour was β = 0.231, SE = 0.056, p < .001. Controlling for the indirect path reduced the direct effect to a marginal level (direct β = 0.048, SE = 0.026, p = .061). The authors tested alternative specifications (adding demographic covariates, adding remaining Big Five traits, and replacing NR subscales with an overall NR score); classic psychedelics remained the only robust predictor of nature relatedness and the NR-Self mediation held across models. Summary interpretation: More frequent lifetime use of classic psychedelics is associated with stronger NR-Self and NR-Experience scores, and the NR-Self dimension largely accounts for the association between psychedelic experience and self-reported everyday pro-environmental behaviour, though a small residual direct effect remains.

Forstmann and colleagues interpret the findings as preliminary evidence that lifetime experience with classic psychedelics is uniquely associated with a stronger internalised identification with nature (NR-Self), and that this identification in turn relates to greater self-reported engagement in a range of pro-environmental behaviours. They note that the pattern is specific: other substance classes did not predict nature relatedness, and among the NR dimensions it was the self-construal facet that uniquely predicted reported ecological actions. The authors emphasise several important limitations. Chief among these is the correlational, cross-sectional design, which precludes causal inference; reverse causality or unmeasured third variables cannot be ruled out. The authors argue theoretically that reverse causation is less plausible—there is no obvious reason why people who already view themselves as part of nature would selectively use classic psychedelics and not other natural psychoactive substances—but they acknowledge that the data cannot empirically exclude this possibility. Second, pro-environmental behaviour was measured by self-report, raising the possibility that findings reflect identity or ideal-self reporting rather than enacted behaviour; the authors recommend future studies include behavioural outcomes (for example, donation tasks) to assess real-world effects. Third, some substance categories had very low prevalence (natural deliriants) limiting analysis, and the Mechanical Turk sample may differ from the general population (for example, on age and education), which could affect generalisability. To address these limitations the authors propose future directions: experimental administration studies and longitudinal within-subject designs to test causality and temporal dynamics; systematic assessment of the setting in which substances are consumed and measurement of experienced ego-dissolution as potential moderators; and use of objective behavioural measures of environmentalism. Finally, Forstmann and colleagues situate the results in a wider context, suggesting that if causal effects are confirmed, psychedelic experiences might constitute one pathway through which people’s wellbeing and pro-environmental behaviour are jointly enhanced, and they note the policy relevance given ongoing debates about the prohibition of these substances. The authors explicitly acknowledge that their findings are tentative and call for further research to validate causal mechanisms and practical implications.