Post-Psychedelic Reductions in Experiential Avoidance Are Associated With Decreases in Depression Severity and Suicidal Ideation

Zeifman and colleagues frame the study within growing interest in serotonergic psychedelics (e.g. psilocybin, LSD, DMT/ayahuasca) as treatments for a range of mental health conditions. Randomised and open-label trials have reported promising reductions in anxiety, depression, substance misuse and suicidal ideation, and prior work suggests that intensity of so-called mystical or peak experiences predicts therapeutic benefit. However, the psychological and neurobiological mechanisms that mediate durable change after psychedelic use remain incompletely understood, and identifying transdiagnostic mechanisms could aid optimisation and targeting of treatments. One candidate transdiagnostic mechanism is reduced experiential avoidance, a process targeted by acceptance and commitment therapy (ACT) and conceptually distinct from general psychological distress. The authors note that prior psychedelic studies using the AAQ-II have shown post‑use reductions but that the AAQ-II may lack discriminant validity from distress. Thus, there is a need to examine changes in the process of experiential avoidance itself and whether such changes relate to decreases in depression severity and suicidal ideation. To address these gaps, the paper reports two prospective cohort studies of individuals planning to use a psychedelic, with the aims of (a) assessing changes in experiential avoidance, depression severity and suicidal ideation after psychedelic use, and (b) testing whether reductions in experiential avoidance are associated with reductions in depression and suicidal ideation. The primary hypotheses were that psychedelic use would be followed by decreases in experiential avoidance, depression severity and suicidal ideation, and that decreases in experiential avoidance would be associated with decreases in the other outcomes.

Both studies used prospective cohort designs enrolling convenience samples of adults planning to use a psychedelic. Participants were recruited online (social media, forums, email) between April 2018 and mid‑2019. Surveys were completed online at baseline (timed to before planned psychedelic use), and at two follow-up points: approximately 2 weeks and 4 weeks after use. Study 1 enrolled 279 people; after exclusions for missing baseline outcome data (n=53), failure to complete both follow-ups (n=97), planned use of non‑serotonergic substances (n=4), and baseline QIDS score of zero (n=4), the final sample was N=104. Study 2 targeted individuals attending psychedelic ceremonies and initially enrolled 478; exclusions for missing baseline outcome data (n=32), failure to complete both follow-ups (n=206), non‑serotonergic planned substances (n=2), and baseline QIDS=0 (n=5) yielded a final sample of N=254. The extracted text does not provide detailed participant demographics because tables were referenced but not included in the extraction. Neither study involved administration of drugs by the investigators; participants self‑reported planned naturalistic psychedelic use. Study 1 included both ceremonial and non‑ceremonial contexts whereas Study 2 specifically recruited attendees of ceremonial ceremonies, described as contexts with facilitators, music, ritual objects and sensory restrictions. The extracted text does not report doses, exact settings, or supervision details beyond the broad ceremonial description. Across studies, planned substances reported included psilocybin/magic mushrooms, LSD/1P‑LSD, ayahuasca, and various DMT derivatives, among others; Study 2 was dominated by psilocybin and ayahuasca reports. Primary measures were the Brief Experiential Avoidance Questionnaire (BEAQ) to assess experiential avoidance, the Quick Inventory of Depressive Symptoms (QIDS) to assess depression severity, and the Suicidal Ideation Attributes Scale (SIDAS) plus the QIDS suicidal ideation item to assess suicidal ideation. Internal consistency (Cronbach's alpha) for the BEAQ and other scales at reported time points was satisfactory (BEAQ baseline a≈0.86–0.89; QIDS baseline a≈0.78–0.85; SIDAS baseline a≈0.82). Because some variables deviated from normality, the investigators used non‑parametric methods where appropriate and constructed an SI composite by summing z‑scores for SIDAS and the QIDS suicidal item to boost power. Primary longitudinal analyses used general linear model repeated measures ANOVAs (with Huynh‑Feldt correction where sphericity was violated) and Bonferroni adjustments for multiple comparisons. Associations between change scores were tested with Spearman's rho. Analyses were conducted in the full samples and in subsamples with baseline QIDS ≥ 6 (mild to very severe depression).

Study 1 (N=104) and Study 2 (N=254) both showed statistically significant decreases in experiential avoidance, depression severity and suicidal ideation after psychedelic use. Study 1: Experiential avoidance (BEAQ) decreased from baseline (M=44.27, SE=1.65) to 2 weeks (M=38.79, SE=1.44; p<.001, d=0.88) and 4 weeks (M=38.35, SE=1.44; p<.001, d=1.07); there was no significant change between 2 and 4 weeks. Depression severity (QIDS) declined from baseline (M=8.25, SE=0.63) to 2 weeks (M=4.24, SE=0.37; p<.001, d=1.41) and 4 weeks (M=3.89, SE=0.36; p<.001, d=1.60), with no significant change from 2 to 4 weeks. Suicidal ideation (SI composite) decreased from baseline (M=0.48, SE=0.26) to 2 weeks (M=-0.19, SE=0.17; p<.001, d=0.86) and to 4 weeks (M=-0.47, SE=0.14; p<.001, d=0.98), with a further significant reduction from 2 to 4 weeks (p=.003, d=0.69). Across the full sample, change in experiential avoidance was significantly correlated with change in depression severity at 2 weeks (Spearman's rho=.371, p<.001) and 4 weeks (rho=.516, p<.001). Change in experiential avoidance was also significantly correlated with change in suicidal ideation at 2 weeks (rho=.371, p<.001) and 4 weeks (rho=.461, p<.001). The extracted text indicates similar significant associations in the subgroup with baseline QIDS ≥ 6, though some subgroup statistics were truncated in the extraction. Study 2: Experiential avoidance (BEAQ) decreased from baseline (M=40.83, SE=0.87) to 4 weeks (M=37.67, SE=0.84; F(1,191)=24.63, p<.001; d=0.72). Depression severity (QIDS) declined from baseline (M=6.24, SE=0.33) to 2 weeks (M=4.29, SE=0.26; p<.001, d=0.97) and 4 weeks (M=3.95, SE=0.24; p<.001, d=1.07), without significant change from 2 to 4 weeks. In the subsample with baseline QIDS ≥ 6 (n=121), depression reductions were larger (baseline M=9.82 to 2 weeks M=5.37, d=1.82; to 4 weeks M=5.11, d=2.09). Suicidal ideation (SI composite) decreased from baseline (M=0.16, SE=0.15) to 4 weeks (M=-0.28, SE=0.10; F(1,191)=12.89, p<.001; d=0.52), with moderate effect sizes in the subgroup with QIDS ≥ 6 (d=0.77). Correlations showed that change in experiential avoidance was significantly associated with change in depression severity at 4 weeks (Spearman's rho=.325, p<.001; subgroup rho=.431, p<.001). Associations between BEAQ change and SI composite change were smaller but statistically significant in the full sample (rho=.154, p=.033) and in the subgroup (rho=.213, p=.045). Across both studies the pattern was consistent: post‑psychedelic reductions in experiential avoidance paralleled reductions in depressive symptoms and suicidal ideation, with effect sizes ranging from small‑moderate to large depending on outcome and subgroup. The extracted text does not report detailed demographic breakdowns or dosing information, nor does it provide clinician‑rated outcomes.

Zeifman and colleagues interpret the findings as evidence that naturalistic psychedelic use—across ceremonial and non‑ceremonial contexts—was followed by reductions in experiential avoidance, depression severity and suicidal ideation that were maintained at least to 4 weeks. The authors highlight that most participants began with subclinical depressive symptoms, and thus the observed changes support the possibility that psychedelic effects may extend across the full dimensional spectrum of depression severity. They further note that reductions in suicidal ideation are noteworthy given limited impact of some first‑line treatments on suicidality. Regarding mechanisms, the investigators argue that decreases in experiential avoidance align with ACT's transdiagnostic model and with prior qualitative and experimental reports of increased acceptance after psychedelics. The observed associations between reductions in experiential avoidance and decreases in depression and suicidal ideation are presented as consistent with the idea that moving from avoidance to acceptance may be a psychological pathway mediating therapeutic benefit. The authors link these psychological changes to prior neurobiological and behavioural findings (e.g. increased amygdala responsiveness, improved emotional processing) and suggest that psychedelics may enhance emotion‑focused coping. The paper states several limitations the authors acknowledge. The studies were uncontrolled convenience cohorts lacking randomisation or placebo control, and attrition could have biased results if individuals with adverse outcomes dropped out. Expectancy, demand characteristics and other biases cannot be excluded, and there were no data quality checks reported. Contextual variables (set and setting), dose, and ceremony characteristics were not tightly controlled or fully recorded in the extracted text. Outcomes relied on self‑report rather than clinician assessment, follow‑up was limited to 4 weeks, and associations between experiential avoidance and clinical outcomes were small to moderate (rho ≈ .154–.516), indicating additional mechanisms likely contribute. The authors therefore recommend controlled trials, longer follow‑ups, clinician‑rated measures and multimodal assessments (including behavioural and neurobiological markers) to test causality and specificity. They also suggest further work to examine specific psychedelics separately, non‑serotonergic compounds, and integration of psychedelics with psychotherapies that directly target experiential avoidance (for example ACT), noting an ongoing trial combining ACT components with psilocybin for major depression (clinicaltrials.gov NCT03429075). In conclusion, the investigators propose that experiential avoidance may be a relevant transdiagnostic mechanism underlying positive outcomes after psychedelic use, but emphasise the need for more rigorous and specific research to confirm and extend these findings.