Psilocybin, psychological distress, and suicidality

Earlier epidemiological analyses found that lifetime use of any classic psychedelic (DMT, ayahuasca, LSD, mescaline, peyote or San Pedro, or psilocybin) was associated with lower odds of recent psychological distress and several measures of suicidality in the US adult population. Those analyses suggested an inverse relationship between classic psychedelic exposure and past month psychological distress, past year suicidal thinking, planning, and attempts, but did not isolate effects of individual substances. Given that psilocybin is the most commonly studied classic psychedelic in contemporary clinical research and a possible candidate for future approved medical use, a substance-specific analysis was needed to clarify whether associations observed for the broader class extend to psilocybin in particular. Hendricks and colleagues therefore set out to evaluate associations between lifetime psilocybin use and four binary outcomes: past month psychological distress, past year suicidal thinking, past year suicidal planning, and past year suicide attempt. The study used pooled, nationally representative survey data to compare mutually exclusive groups defined by lifetime psychedelic use in order to assess whether psilocybin-only use shows distinct relationships with distress and suicidality relative to use of other psychedelics or no psychedelic use.

The investigators analysed pooled data from the National Survey on Drug Use and Health (NSDUH) for survey years 2008 through 2012. The analytic sample comprised adult respondents aged 18 or older with valid data on the variables of interest; the total unweighted sample reported in the extracted text was 191,832 respondents. To examine substance-specific associations, four mutually exclusive groups were created: (1) Psilocybin Only (lifetime psilocybin use but no other classic psychedelic), (2) Psilocybin & Other Psychedelics (lifetime psilocybin plus other classic psychedelics), (3) Non-Psilocybin Psychedelics Only (lifetime use of classic psychedelics other than psilocybin), and (4) No Psychedelics (no lifetime use of any classic psychedelic). Primary outcomes were binary indicators: past month psychological distress (yes/no), past year suicidal thinking (yes/no), past year suicidal planning (yes/no), and past year suicide attempt (yes/no). The analysis approach described in the extracted text used multivariate logistic regression to evaluate associations between group membership and each outcome, with planned pairwise contrasts among the four groups. The report provides Wald chi-square statistics and p-values for overall group effects and summarises planned comparisons. The authors discuss a methodological debate about covariate adjustment, noting criticism from other researchers that controlling for lifetime use of other illicit substances could constitute overadjustment if such substance use were on the causal path from psychedelic exposure to outcomes. Hendricks and colleagues argued that there is no clear evidence that classic psychedelic use causes other illicit drug use and that controlling for other illicit substance use is appropriate to account for known suicide risk factors (for example, substance misuse and impulsive-aggressive personality traits). The extracted text does not provide a full list of covariates included in the models, nor does it detail handling of survey design features or weighting beyond reporting some weighted percentages.

Of 191,832 respondents, group membership distributions reported in the extracted text were: Psilocybin Only 7,550 (2.47% weighted), Psilocybin & Other Psychedelics 12,724 (6.49% weighted), Non-Psilocybin Psychedelics Only 6,963 (4.59% weighted), and No Psychedelics 164,595 (86.42% weighted). In multivariate logistic regression models, overall group membership was significantly associated with each outcome: past month psychological distress (Wald chi-square = 24.41, p < .0001), past year suicidal thinking (Wald chi-square = 17.85, p = .0005), past year suicidal planning (Wald chi-square = 26.13, p < .0001), and past year suicide attempt (Wald chi-square = 10.95, p = .01). Planned comparisons indicated that the Psilocybin Only group had reduced odds for all four outcomes relative to the No Psychedelics group. Compared with the Psilocybin & Other Psychedelics group, Psilocybin Only had decreased odds of past year suicidal thinking and past year suicidal planning. Relative to the Non-Psilocybin Psychedelics Only group, Psilocybin Only showed reduced odds of past month psychological distress. The authors also report that both the Psilocybin Only and Psilocybin & Other Psychedelics groups exhibited reduced odds for all outcomes except past year suicidal planning when compared with the No Psychedelics group; additionally, reductions in past month psychological distress were observed for the Psilocybin Only and Psilocybin & Other Psychedelics groups in comparisons involving the Non-Psilocybin Psychedelics Only group. Specific effect estimates such as adjusted odds ratios and confidence intervals for these contrasts are not provided in the extracted text. The authors interpret the pattern of contrasts as indicating that lifetime psilocybin use, and particularly psilocybin use without other classic psychedelic use, is associated with lower likelihood of psychological distress and suicidality in this cross-sectional survey sample.

Hendricks and colleagues interpret the results as evidence that the associations between classic psychedelic use and lower psychological distress and suicidality reported in prior work extend to psilocybin specifically. They highlight that many of the strongest contrasts involved the Psilocybin Only group, which the authors suggest may indicate that psilocybin has especially favourable associations with mental health outcomes among classic psychedelics. The paper situates these findings in relation to prior literature suggesting therapeutic potential and a favourable safety profile for psilocybin. The authors address a methodological critique regarding overadjustment for other illicit substance use, arguing that controlling for such covariates is appropriate because there is no clear evidence that classic psychedelic use causes other illicit drug use and because those covariates capture established suicide risk factors. They contend that inclusion of these covariates likely does not introduce overadjustment bias in their analyses. In terms of implications, the authors propose that the observed associations are consistent with renewed clinical research into psilocybin for conditions such as cancer-related anxiety and depression and for addictive disorders, and they state that the data do not support a public safety concern that controlled clinical prescription of psilocybin would increase suicide risk. The extracted text does not present an explicit list of study limitations or cautionary notes beyond the discussion of covariate adjustment, nor does it claim causal effects; the results are framed as associations from a large, cross-sectional national survey that may inform regulatory and clinical considerations.