Peri-traumatic consumption of classic psychedelics is associated with lower anxiety and post-traumatic responses 3 weeks after exposure

Earlier research has highlighted potential therapeutic effects of psychedelic compounds for post-traumatic stress, but the neurobiological mechanisms that might mediate these effects remain unclear. Classic psychedelics (for example LSD and psilocybin) and MDMA engage overlapping but distinct neurotransmitter and receptor systems, and experimental work suggests they may differently affect the encoding and consolidation of fear memories. Extending these laboratory and animal findings to real-life trauma exposure is an important gap in the literature. Karp Barnir and colleagues used a naturalistic opportunity to compare outcomes following peri-traumatic use of different recreational psychedelics. They assessed survivors of a mass terrorist attack at a music festival who, in the hours before the assault, had consumed either classic psychedelics, MDMA, or no psychedelics, and measured anxiety and acute post-traumatic symptoms three weeks after the event to test whether peri-traumatic compound type was associated with differences in early trauma responses. The authors frame this as informative for understanding mechanisms that could influence eventual PTSD trajectories and for identifying pharmacologic targets relevant to trauma memory formation.

Data collection took place during 22–28 October 2023, approximately three weeks after an attack on attendees of the Nova music festival. Survivors attending an ad hoc “Healing Space” were approached in person by the first author, a volunteering clinical psychologist, and invited to complete an anonymous questionnaire about substance use and current mental health. Of roughly 500 healing-space attendees, 400 were approached and 343 survivors (189 women; age range 18–64, mean 25.51, SD 5.30; 86% response rate) provided informed consent and completed the survey. The study received institutional ethics approval. The extracted text does not report demographic details for the 57 people who declined participation, so potential differences between responders and non-responders are unknown. Participants indicated whether they had consumed any of 18 listed mind-altering substances during the festival and recorded the hour of consumption; the authors note that all participants who reported ingesting a psychedelic did so 1–5 hours before the attack. Reported substances included cannabis (n = 133), alcohol (n = 147), MDMA (n = 124), ketamine (n = 46), LSD (n = 31), mushrooms (n = 6), mescaline (n = 13), among others. No participants reported use of DMT, GHB, cocaine, opioids, ayahuasca, ibogaine, or salvia divinorum. Two self-report outcome measures were administered: current anxiety with the 7-item GAD-7 (sample Cronbach α = 0.88) and acute post-traumatic symptom severity with the 24-item Acute Stress Disorder Scale (ASDS; sample Cronbach α = 0.92). Item averages formed total scores (GAD-7 range 0–3; ASDS range 1–5), with higher scores indicating greater symptom severity. For analysis, participants were grouped into three peri-traumatic exposure categories: at least one classic psychedelic (mushrooms, LSD, DMT, 2C-B, mescaline, ayahuasca, ibogaine, or salvia; n = 40), MDMA (n = 120), and no psychedelics (n = 179); four participants who consumed both classic psychedelics and MDMA were excluded from group analyses. The primary analytic approach used analyses of variance (ANOVA). Initial one-way ANOVAs tested Group (classic psychedelics, MDMA, none) effects on GAD-7 and ASDS scores. Because many participants also used other recreational substances (primarily alcohol and cannabis), the authors additionally coded participants by whether they consumed other substances (yes/no) and conducted two-way ANOVAs testing Group × other-substances interactions for each outcome. A Bonferroni correction for the two main dependent variables set the significance threshold at 0.025. Supplementary two-way ANOVAs examined potential moderators including gender, age (median split), history of psychiatric disorder, and past-year classic psychedelic use. The text notes that peri-traumatic consumption in the three weeks after exposure could not be examined due to very small numbers.

Anxiety: Across the sample the mean GAD-7 score was 1.90 (SD = 0.77). The one-way ANOVA showed a significant main effect of Group on anxiety, F(2, 333) = 4.25, p = 0.015, η2 = 0.026. Participants who had been under the influence of classic psychedelics during the attack reported lower anxiety three weeks later (mean GAD-7 = 1.59) than participants in the MDMA group (mean = 1.91), with a reported contrast F(1, 158) = 5.87, p < 0.001, and lower than the no-psychedelics group (mean = 1.98), F(1, 217) = 9.15, p < 0.001. There was no significant difference between the MDMA and no-psychedelics groups (p = 0.441). The Group × other-substances interaction on anxiety was not significant, indicating that concurrent use of other recreational substances did not moderate the association between psychedelic group and anxiety. Supplementary analyses tested whether the association between peri-traumatic classic psychedelic use and lower anxiety was moderated by gender, age, prior psychiatric diagnosis (53 reported such a diagnosis), or past-year classic psychedelic use (112 reported prior-year use). Peri-traumatic classic psychedelic use had significant associations with gender, age, and past-year use (chi-square tests reported), but the main effect on anxiety remained statistically significant after controlling for these variables and none of the interaction terms were significant. Specifically, peri-traumatic classic psychedelic consumption was more common among women than men (15.51% vs 7.24%), among participants older than 25 than younger participants (20.83% vs 6.85%), and among those reporting classic psychedelic use in the year before the festival (24.11% vs 5.73%). Past psychiatric disorder was not associated with peri-traumatic classic psychedelic use. Post-traumatic symptoms (ASDS): The mean ASDS score across the sample was 3.27 (SD = 0.75). The overall main effect of Group on ASDS scores was not significant, F(2, 331) = 0.56, p = 0.573. However, there was a significant Group × other-substances interaction, F(2, 331) = 4.26, p = 0.014, η2 = 0.027. Follow-up tests showed that among participants who did not consume additional recreational substances (n = 151), Group differences were significant, F(2, 148) = 3.87, p = 0.023, η2 = 0.023: within this subgroup, those under the influence of classic psychedelics reported lower post-traumatic symptom severity than the MDMA group, F(1, 92) = 5.45, p < 0.001, and lower than the no-psychedelics group, F(1, 111) = 7.36, p < 0.001. No differences between groups were observed among participants who did consume additional substances. Additional moderator analyses within the no-other-substances subgroup indicated the main effect of peri-traumatic classic psychedelic consumption on ASDS remained significant after controlling for gender, age, past psychiatric disorder, and past-year psychedelic use, and interactions were not significant. Other reported details: the authors note they could not analyse the moderating effect of classic psychedelic consumption during the three weeks after exposure because very few participants reported such use (eight for anxiety analyses; five for ASDS analyses). The extracted text does not report dose or purity measures for substances consumed.

Karp Barnir and colleagues interpret their findings as evidence that peri-traumatic consumption of classic psychedelics was associated with reduced anxiety and, when not combined with other recreational drugs, reduced acute post-traumatic responses three weeks after a severe trauma. They suggest that these associations may reflect differential engagement of neurobiological systems by classic psychedelics versus MDMA, noting, for example, the strong affinity of classic psychedelics for 5-HT2A receptors and the role of serotonergic signalling in memory consolidation as a plausible pathway through which trauma memory encoding and maintenance could be modulated. The authors also report that concurrent consumption of other recreational substances, especially alcohol and cannabis, appeared to attenuate the protective association between classic psychedelics and post-traumatic symptoms. They propose that drug–drug interactions affecting memory processes and emotion regulation may partly explain this moderating effect. In comparing their results to an unpublished study that reported protective associations for peri-traumatic MDMA use, the authors highlight methodological differences that could account for discrepant findings: differing follow-up windows (their focus on the acute three-week period), variations in substance classification, consideration of poly-substance use, and differing emphases on social-support or sleep-related mechanisms versus direct symptom measures. The authors acknowledge several limitations. Findings are based entirely on self-report measures; objective physiological or behavioural data were not collected. Follow-up was limited to three weeks, so claims about longer-term PTSD trajectories cannot be made. The recruitment framing—explicitly asking about substance use—may have introduced selection bias, potentially favouring respondents with more favourable experiences or greater willingness to disclose illegal drug use; the illegality of psychedelics in Israel could have further influenced willingness to report. Pre-trauma baseline measures were unavailable, so causal inferences about the effect of peri-traumatic psychedelic use on subsequent symptoms are limited. Finally, the authors could not verify dosage or purity of substances consumed in the field, preventing dose–response analyses. They note, moreover, that controlled clinical trials of classic psychedelics for PTSD are not yet established, and caution that psychedelics may help some individuals while harming others when used outside controlled therapeutic settings.