Classic psychedelics, health behavior, and physical health

Earlier research has reported associations between lifetime use of classic psychedelics (serotonin 2A receptor agonists such as mescaline and psilocybin) and better physical health in population samples, including lower odds of overweight/obesity and of conditions such as heart disease, diabetes, and hypertension. It is plausible that such associations could be mediated, at least in part, by changes in health behaviour; qualitative and cross-sectional studies have reported spontaneous improvements in diet, exercise, and substance use following psychedelic experiences, and several measures of the acute psychedelic experience (for example, mystical experience and ego-dissolution scales) predict longer-term outcomes. Recent work identifies psychological insight as a potentially important common feature of the psychedelic experience, but its relationship to health behaviour and physical health has not been examined in a nationally representative sample free of pronounced self-selection bias. Simonsson and colleagues set out to test whether lifetime classic psychedelic use and the degree of psychological insight reported for respondents' single most insightful psychedelic experience are associated with multiple domains of health behaviour (tobacco, alcohol, diet, exercise) and with markers of physical health (body mass index categorised as healthy versus not, and a composite of noncommunicable disease (NCD) in the past year). Using a US adult sample representative on sex, age, and ethnicity, the authors hypothesised that lifetime use and greater psychological insight would each be associated with healthier behaviours, higher odds of healthy BMI, and lower odds of recent NCD.

The investigators preregistered their hypotheses and analysis plan and aimed to recruit approximately 2,800 US residents aged 18 or older through the Prolific Academic platform between 1 October and 9 October 2021; the final target was based on power calculations anticipating about 395 lifetime classic psychedelic users. Prolific's representativeness function was used to stratify the sample on sex, age (five bands), and ethnicity to approximate the US adult distribution. Participants provided digital informed consent, completed demographic and substance-use questions, and answered measures of health behaviour and health status. Study completion payment was US$2.20; 131 participants did not complete the study. Procedures were deemed exempt by the University of Wisconsin–Madison IRB. Measures included demographics (age, gender, ethnoracial identity, sexual orientation, education, household income, marital status, self-reported engagement in risky behaviour) and lifetime use of a range of substances. A technical error meant data were not collected for lifetime use of other stimulants, heroin, and tranquilizers. Lifetime classic psychedelic use was assessed by asking about ayahuasca, DMT, LSD, mescaline, peyote, San Pedro, and psilocybin; respondents endorsing any of these were coded as lifetime users. Among users (n = 613), psychological insight during their single most insightful psychedelic experience was measured with the 23-item Psychological Insight Questionnaire (PIQ), producing a total score and two subscales: Avoidance and Maladaptive Patterns (AMP) and Goals and Adaptive Patterns (GAP). The PIQ and subscales were z-scored for analyses. Health-behaviour assessments comprised validated brief instruments: the 7-item Fagerström Test for Cigarette Dependence (scores reverse-scored so higher values indicate healthier tobacco behaviour), the 3-item AUDIT-C for alcohol (reverse-scored), the 7-item International Physical Activity Questionnaire—Short Form (IPAQ-SF) categorised into low/medium/high activity, and the 8-item Starting the Conversation scale for dietary quality (reverse-scored so higher scores reflect healthier diet). Height and weight were self-reported to calculate BMI, dichotomised as healthy (18.5–25) versus not. A binary composite variable captured whether a respondent had been told by a doctor in the past 12 months that they had cancer, heart disease, high blood pressure, or type 2 diabetes (NCD in the past year). Author-constructed slider items (0–100) asked lifetime users whether they thought their most insightful psychedelic experience and subsequent contemplation led to changes in overall health behaviour and domain-specific behaviours. Statistical analyses used linear regression for alcohol-, tobacco-, and diet-related behaviour outcomes, ordered logistic regression for exercise categories, and logistic regression for binary BMI and NCD outcomes. Models controlled for a wide set of demographic and substance-use covariates (age bands, gender categories including transgender/non-binary, ethnoracial identity, sexual orientation, education, household income bands, marital status, lifetime engagement in risky behaviour, lifetime use of specified drugs and tobacco products, and age of first alcohol use). PIQ scores and subscales were standardised to aid comparison. The extracted text indicates supplemental tables reported descriptive statistics and exploratory analyses.

The sample targeted the preregistered size (N = 2,822 as reported earlier) and included 613 respondents who reported lifetime classic psychedelic use; non-completers numbered 131. Descriptive comparisons (reported in supplemental material) showed lifetime psychedelic use was more common among men, those reporting greater engagement in risky behaviour, and respondents with lifetime use of other illicit substances. In covariate-adjusted regression models, lifetime classic psychedelic use was associated very modestly with healthier tobacco-related behaviour and healthier diet-related behaviour, but it was not associated with alcohol-related behaviour or exercise-related behaviour. Within the subgroup of lifetime users (n = 613), higher PIQ total scores and both PIQ subscales (AMP and GAP) were each modestly associated with higher odds of healthier exercise-related behaviour. Greater GAP scores were also modestly associated with healthier diet-related behaviour; other direct associations between insight measures and tobacco or alcohol behaviours were not observed in these models. When analysing health-behaviour change attributed by respondents to their single most insightful psychedelic experience, greater PIQ total, AMP, and GAP scores were moderately to strongly associated with participants reporting greater overall health-behaviour improvements. These insight measures were modestly associated with self-reported improvements in diet and exercise attributed to that experience. Greater PIQ total and AMP scores were also modestly associated with alcohol-related behaviour improvements attributed to the experience. None of the models showed associations between insight measures and tobacco-related improvements. Regarding physical health outcomes, lifetime classic psychedelic use was not associated with having a healthy BMI or with NCD in the past year. By contrast, higher PIQ total scores and both subscales were each associated with modestly higher odds of having a healthy BMI. No association was observed between either lifetime use or psychological insight and NCD in the past year. The authors note additional exploratory results in supplemental tables but do not provide numerical effect sizes or confidence intervals in the extracted text.

Simonsson and colleagues interpret the results as suggesting that psychological insight experienced during a classic psychedelic episode may contribute to positive health-behaviour change and to better physical health in some domains. They highlight the most consistent pattern in the data: links between psychological insight (PIQ total and subscales) and healthier diet and exercise behaviours, and higher odds of a healthy BMI. Given the relevance of diet, exercise, and BMI to obesity and its health consequences, the authors propose that classic psychedelics warrant further investigation as a potential avenue in weight-management research, particularly where treatments can be designed to promote insight (for example, by integrating meditative practices to cultivate self-knowledge). The authors characterise the associations with alcohol- and tobacco-related behaviours as less clear-cut. They note that prior studies documenting cessation effects recruited participants with problematic substance use, whereas the present sample was more representative and likely contained many respondents without substance problems; floor effects and differences in sample composition may therefore account for null or mixed findings. The null association between lifetime psychedelic use and physical-health indicators contrasts with prior large national studies; the authors caution that earlier investigations had much larger sample sizes (providing far greater statistical power) and used different variable coding (for example, BMI coded across six categories rather than dichotomised here), limiting comparability. Several limitations are acknowledged. The sample was stratified on sex, age, and ethnicity but did not appear representative on socioeconomic indicators such as education and household income; the prevalence of lifetime classic psychedelic use in the sample (22%) exceeded the 14% reported in the US National Survey on Drug Use and Health, possibly reflecting higher socioeconomic status of the Prolific sample or underestimation of some substances in NSDUH. The questionnaire omitted items on set and setting for the most insightful experience, preventing analysis of context-dependent contributors to insight and subsequent behaviour change. Crucially, the cross-sectional design precludes causal inference: it is equally possible that healthier people are more likely to have used psychedelics and to report insight, or that unmeasured confounders (for example, personality traits) account for associations. The authors recommend longitudinal studies and randomised controlled trials to clarify causal pathways and to test whether eliciting psychological insight mediates health-behaviour and physical-health outcomes.

The authors conclude that, while classic psychedelics have been preliminarily linked to mental-health benefits, their effects on health behaviour and physical health are less well understood. The present study's findings indicate that the subjective experience of psychological insight elicited by classic psychedelics may be associated with positive health-behaviour change and better physical health in specific domains, particularly those related to weight management. The paper is presented as a springboard for future longitudinal research and randomised controlled trials to interrogate potential causal pathways between classic psychedelic use, psychological insight, health behaviour change, and physical health.