Exploring the Credibility of Psilocybin-assisted Therapy and Cognitive-behavioral Therapy for Depression

Altman and colleagues situate the study within literature showing that patients' pre-treatment beliefs and expectancies influence therapeutic outcomes, and note persistent limitations of current depression treatments including limited efficacy for some patients, side effects of antidepressant medication, cost and access barriers for psychotherapy, and slow onset of benefit. They describe renewed interest in psychedelic-assisted therapies—particularly psilocybin-assisted therapy (PAT)—and cite early clinical work suggesting rapid antidepressant effects, but emphasise that much of that literature is preliminary, with small samples and short follow-up. The authors note a gap in knowledge about lay impressions of PAT relative to established psychotherapies, and the potential importance of those impressions for uptake and outcomes. This study therefore set out to compare perceived credibility of cognitive-behavioural therapy (CBT) and psilocybin-assisted therapy among people reporting depressive symptoms. Using a vignette approach, the investigators examined overall credibility ratings for each treatment and tested whether demographics, prior psychotherapy, lifetime hallucinogen use, and familiarity with the treatments predicted credibility. They hypothesised that, despite publicity around psychedelics, CBT would be rated as more credible than PAT.

Participants were recruited via Amazon Mechanical Turk and had to be aged 18 or older, English-speaking, and current US residents. Of 1,489 who started the survey, the study excluded 295 people who reported minimal depressive symptoms, 177 who terminated the survey early, and 214 who failed comprehension checks, leaving a final sample of 803. The University at Albany Institutional Review Board approved the procedures. Measures included self-reported demographics and mental health service history, lifetime and recent hallucinogen use (including psilocybin), and depressive symptoms assessed with the CESD-10, a 10-item short-form of the Center for Epidemiological Studies Depression Scale. The CESD-10 was scored 0–30 with higher scores indicating more symptoms; participants scoring below 4 were excluded and the retained sample had a mean CESD-10 > 15 (SD = 5.80, range 4–30). The authors report satisfactory internal consistency for measures used. Treatment familiarity and credibility were assessed with a vignette procedure. Participants provided baseline familiarity ratings (0–100) for CBT and PAT, then read descriptions of each treatment; the order was randomly counterbalanced. The CBT vignette described standard CBT components, a short-term course (12–20 weeks), and an improvement rate of 50–65%. The PAT vignette described preparatory sessions, two five-hour dosing sessions up to two weeks apart with guides, and reported rapid symptom reductions (near 50% at one week; >50% no longer meeting depression criteria at one month). Clinicians with relevant expertise reviewed the vignettes, and comprehension checks followed the descriptions. Credibility was measured using six items (e.g. logicality, expected success, confidence recommending, likelihood of uptake by others and self, overall effectiveness), each rated 0–100 and summed to a global credibility score; Cronbach's alphas were .908 for CBT and .937 for PAT. For analysis the researchers used paired t-tests to compare CBT and PAT credibility, bivariate correlations and t-tests for subgroup comparisons, and multiple regression to identify independent predictors of credibility. They removed one multivariate outlier and applied a Bonferroni-adjusted significance threshold of p = .001 to limit Type I error. Adjusted degrees of freedom were used where Levene's test indicated unequal variances.

The primary finding was that CBT was rated as more credible than PAT. Mean global credibility for CBT was 393.27 (SD = 109.78, range 6–600) compared with 309.89 for PAT (SD = 142.94, range 0–600); the paired t-test was t(800) = 14.50, p < .001, Cohen's d = .51. Baseline familiarity before reading vignettes was also higher for CBT (M = 49.70, SD = 31.94) than for PAT (M = 26.44, SD = 28.48), t(715) = 17.90, p < .001, Cohen's d = .66. Bivariate subgroup comparisons showed that men rated PAT as more credible than women (Men M = 332.86, SD = 128.74; Women M = 290.77, SD = 150.85; t ≈ 4.22, p < .001, Cohen's d = .30), whereas CBT credibility did not differ by gender after the Bonferroni correction. Participants with prior psychotherapy rated CBT as more credible than those without (Therapy M = 414.63, SD = 104.60; No therapy M = 376.50, SD = 112.14; t ≈ 4.87, p < .001, Cohen's d = .35). Lifetime hallucinogen users rated PAT as more credible than non-users (Hallucinogen M = 366.21, SD = 126.28; No hallucinogen M = 285.92, SD = 143.67; t ≈ 7.67, p < .001, Cohen's d = .59). Credibility ratings did not differ by racial identity for either treatment. Correlation analyses highlighted notable associations: PAT credibility correlated with lifetime hallucinogen use (r = .251) and with familiarity with psychedelic treatment (r = .451). CBT credibility correlated with CBT familiarity (r = .322). Familiarity ratings for the two therapies were positively correlated (r = .342). In multiple regression models predicting credibility, the equation for CBT credibility was significant (F(8,615) = 12.66, p < .001), but CBT familiarity was the only significant predictor (standardised Beta = 0.356, p < .001). For PAT credibility the regression was also significant (F(8,615) = 19.48, p < .001), with familiarity with psychedelic treatment the only unique predictor (standardised Beta = 0.365, p < .001). The authors note they excluded one multivariate outlier prior to regression and used transformed age to correct skew where required.

Altman and colleagues interpret the results as indicating that, among people reporting depressive symptoms recruited online, CBT is perceived as more credible than psilocybin-assisted therapy, and that familiarity with a given treatment is the strongest predictor of its perceived credibility. They link these findings to prior work showing that treatment beliefs relate to uptake and outcomes, and suggest that clinicians and researchers should consider patients' familiarity and beliefs when discussing treatment options. The study team observed that male gender and lifetime hallucinogen use were associated with higher PAT credibility in bivariate analyses, but that these associations appeared to operate through greater familiarity with PAT; in regression models only familiarity remained a significant predictor. They highlight that CBT's superior credibility aligns with previous findings comparing CBT to rapid-onset biological treatments, and suggest that widespread media attention to psychedelics has not evidently inflated lay credibility for PAT in this sample. Several limitations are acknowledged. Data were collected online and relied on self-report, so participants may have misrepresented depressive symptoms or drug use. The credibility scales, while brief and internally consistent, lack nuance; credibility scores exhibited wide ranges. The vignette comparison focused on PAT versus CBT only, limiting inferences about other psychotherapies or pharmacological treatments. The extracted text also notes that the study could not fully parse race and ethnicity effects and that further qualitative and more detailed quantitative work is needed to explore how specific diagnoses and types of hallucinogen exposure (e.g. recreational versus supervised) relate to credibility. Practical implications reported by the authors include the value of clinician education efforts and collaborative decision-making with clients, as increased and accurate familiarity with PAT may alter acceptability. They also point to ongoing therapist training efforts for psychedelic-assisted interventions and recommend continued research in larger and more diverse samples to inform dissemination and implementation. The investigators conclude that while PAT may hold promise, it is not yet perceived as universally credible and clinicians should provide accurate information about all evidence-based options.