Psychedelics not linked to mental health problems or suicidal behavior: A population study.

Johansen and colleagues frame the study within the literature on classical serotonergic psychedelics (LSD, psilocybin, mescaline), noting these drugs share a primary action at the 5-HT2A receptor, produce similar subjective effects and show cross-tolerance. The authors summarise prior evidence that psychedelics are not known to cause organ damage, compulsive use or addiction, that serious acute injuries are rare, and that controlled trials and studies of religious use have not demonstrated lasting harms. They also outline the long history of non-medical and ritual use, growing therapeutic interest, and the contested nature of national and international prohibition, which has constrained research. Using a large, nationally representative dataset, the study sets out to re-examine whether lifetime use of classical psychedelics is associated with a range of past-year mental health problems. In particular, the investigators extend their earlier population analysis by including measures of suicidal thoughts, plans and attempts, and by adjusting for sociodemographics, other drug use and childhood depression to test whether psychedelic use is an independent risk factor for mental health problems at the population level.

The researchers pooled publicly available data from the US National Survey on Drug Use and Health (NSDUH) for the years 2008–2011, restricted to respondents aged 18 years and over. After exclusions (approximately 10% removed from the public use file for anonymity or excessive missing data) the analytic sample comprised 135,095 respondents, of whom 19,299 reported lifetime use of a psychedelic substance. The overall survey response rate was 78%. The authors note that half of 2008 and earlier years were not pooled because of questionnaire differences, including absence of suicidal behaviour questions. Psychedelic exposure was defined primarily as lifetime use of LSD, psilocybin, mescaline or peyote; mescaline and peyote were combined for some analyses and peyote was also examined separately. Past-year use data were available only for LSD. The study examined 11 self-reported past-year mental health indicators, including serious psychological distress assessed by the K6 scale, mental health treatment (inpatient, outpatient, psychiatric medication prescription, and perceived need but not receiving treatment), symptoms and diagnoses of depression and anxiety, and suicidal thoughts, plans and attempts. Control variables comprised a range of sociodemographic, psychological and other drug use covariates selected on the basis of prior associations with mental health. Compared to their previous analysis, the present data allowed inclusion of self-reported depressive episode before age 18; a measure of lifetime exposure to an extremely stressful event was not available. Multivariate logistic regression models were used to estimate adjusted odds ratios (aORs) for associations between mental health outcomes and (a) any lifetime psychedelic use, (b) lifetime use of specific substances (LSD, psilocybin, mescaline/peyote, peyote), and (c) past-year LSD use. Analyses were also stratified by sex, age, past-year illicit drug use and childhood depressive episode. The authors report that all unstratified analyses met a rule of thumb of 25 or more events per control variable and that stratified analyses had at least eight events per control variable; variance inflation factors for control variables were under 2.5, indicating little multicollinearity. The extracted text does not provide the full list of control variables or the precise definition of all 11 mental health indicators within the prose; these appear in figures and tables referred to but not fully reproduced in the extraction.

Psychedelic users differed from non-users on several background characteristics: they were more likely to report a depressive episode before age 18, to be younger, male, white, unmarried, to report higher education and income on average, to endorse risk-taking, and to have used other drugs. In adjusted analyses, lifetime use of any psychedelic was not associated with increased likelihood of any examined past-year mental health problem. The aORs for associations with mental health outcomes generally lay in the range 0.7–1.1, and all were small (the authors note aOR < 1.2 in all cases). One statistically significant finding was a lower likelihood of past-year inpatient mental health treatment among lifetime psychedelic users (aOR 0.8, 95% confidence interval 0.6–0.9, p = 0.01); this finding differed from the authors' prior study, where the association was not statistically significant. Sensitivity checks that included respondents with missing data (imputed to the most common response) or excluded Native Americans did not materially change the results. Analyses of specific substances produced more granular results: the authors report ten associations between particular psychedelic exposures and a reduced likelihood of various mental health problems, and one association indicating increased likelihood. Several associations with lower likelihoods were statistically significant for psilocybin, including reduced odds of past-year serious psychological distress, inpatient treatment and psychiatric medication prescription, though the extracted text contains incomplete numerical reporting for some of these estimates. Mescaline/peyote use showed a weakly statistically significant association with increased likelihood of past-year symptoms of major depressive episode (aOR 1.2, p = 0.02), but mescaline/peyote was not associated with a diagnosis of depression (aOR 1.0, p = 0.59), and peyote use alone was not associated with depressive symptoms or diagnosis. Stratified subgroup analyses yielded eight associations between psychedelic use and decreased likelihood of certain past-year mental health problems, most with weak statistical significance and none that matched patterns from the authors' previous study. Notably, among respondents who reported a depressive episode before age 18, lifetime psychedelic use was associated with lower odds of past-year suicidal thoughts (aOR 0.8, p = 0.01) and suicidal plans (aOR 0.5, p = 0.002). Overall, the study did not find any association between lifetime psychedelic use and increased likelihood of past-year serious psychological distress, mental health treatment, depression, anxiety, or suicidal thoughts or behaviour. The authors also report no population-level support for links between psychedelic use and 'flashbacks' or hallucinogen persisting perceptual disorder (HPPD): lifetime psychedelic use and past-year LSD use were not associated with past-year visual phenomena, panic attacks, psychosis or overall serious psychological distress. The extracted text summarises these results alongside references to evidence from clinical trials and ceremonial use studies indicating rare or absent reports of persistent adverse perceptual symptoms.

Johansen and colleagues interpret their findings as failing to support the hypothesis that lifetime use of classical psychedelics is an independent risk factor for a range of past-year mental health problems, including suicidal thoughts and behaviours. They highlight consistency with their earlier population study and with recent randomised clinical trials and observational studies of ritual use, arguing that the epidemiological signal for harm at a population level is absent or weak. The authors offer several possible explanations for the pattern of results: true null effects, a population-level beneficial effect for some users, selection effects whereby people who use psychedelics have relatively better pre-existing mental health, or chance findings among some subgroup analyses. The discussion contrasts population-level evidence with case reports and theoretical concerns such as HPPD, noting that many of the classic anecdotes and earlier claims of widespread harm are not borne out in representative survey data or contemporary clinical trials. At the same time, the authors explicitly acknowledge the limitations of their data: the cross-sectional, retrospective design prevents causal inference; important potential confounders (for example, family psychiatric history) were unavailable; timing of psychedelic exposure relative to mental health outcomes could not be established; and measures were screening questions rather than diagnostic interviews. They also note reliance on self-report, lack of dose, purity and setting information, inability to identify DMT use, absence of institutionalised populations (such as a small fraction of prison, hospital or military populations) from the sample, and that the study did not correct for multiple comparisons so some weak associations may be due to chance. In light of these caveats the investigators stop short of claiming psychedelics are therapeutically protective, but they emphasise that the data do not justify viewing lifetime psychedelic use as a major population-level risk factor for mental health problems. The authors situate these empirical findings within a broader historical and policy commentary, observing that early prohibitions were influenced by cultural and political forces rather than systematic harm assessment, and concluding that the public-health rationale for prohibition is difficult to sustain based on current evidence.

The authors conclude that their results align with prior population research, recent randomised trials and observational studies of ceremonial use in finding little evidence that lifetime use of classical psychedelics is linked to lasting mental health problems. They emphasise that, judged statistically at the population level, psychedelic use does not appear to be particularly hazardous compared with many common activities, and they argue that prohibition of these substances is difficult to justify from a public health or human rights perspective. The authors reiterate the need to consider risks in a statistical framework rather than relying on anecdote or isolated case reports.