A new paper argues psychedelic research built its main outcome measure on a mistake. The fix is a rename, not a retraction.

The Mystical Experience Questionnaire sits inside nearly every major psychedelic trial as a primary or secondary endpoint. A new review traces its lineage back to a specific, largely unexamined mid-century framework and argues the field inherited a religious category it never should have adopted as science. The proposed fix is more useful than the critique alone: rename the instrument, and use the version its own original architect built later.

Nearly every major psychedelic trial this desk has covered uses some version of the same instrument to help explain why the drug worked, a measure of whether the participant had a “mystical experience” during the session. A new review in Psychopharmacology, by Richard Saville-Smith and Sharday Mosurinjohn, argues the field built that measurement on a specific historical mistake, and that the fix is not to abandon the tool but to rename and reorient it around the work of the very researcher who built it.

The argument, precisely

The paper’s target is the Mystical Experience Questionnaire, the widely used instrument that scores dimensions like unity, sacredness, and ineffability during a psychedelic session, and whose scores are repeatedly reported as correlating with therapeutic outcomes across trials in depression, addiction, and end-of-life distress. The authors trace the questionnaire’s conceptual roots to the mid-century work of philosopher Walter Stace and, more directly, physician and minister Walter Pahnke, whose 1962 “Good Friday Experiment” framework treated psychedelic states as instances of a specific, cross-culturally universal religious category. The paper’s core claim is that this foundational framework was, in the authors’ words, flawed and largely unexamined, and that contemporary trials have adopted its vocabulary and its assumptions without re-litigating whether the underlying category holds up.

The paper is structured in two parts. The first, which the authors call an archaeology, re-examines Stace’s and Pahnke’s original texts directly. The second, a genealogy, traces how the specifically religious concept of mysticism became attached to psychedelic research and normalized across what the authors term second-generation psychedelic research, broadly the current clinical-trial era.

The proposed fix

Rather than arguing the instrument should be discarded, the paper proposes renaming it: from the Mystical Experience Questionnaire to a Psychedelic Experience Questionnaire. The authors frame this as more than semantic. They argue it would actually better honor Pahnke’s own intellectual trajectory, since his later work moved toward a broader, five-part typology of psychedelic experience rather than the narrower religious framework his earlier work is now remembered for. The rename, in this argument, liberates the measurement from what the authors call a dubious legacy in which therapeutic outcomes get correlated with a mystical-experience score, then interpreted as evidence that psychedelic therapy works because it occasions something quasi-religious, rather than testing that assumption directly.

Why this is not just a semantic argument

A rename sounds like the mildest possible critique, but the underlying claim has real teeth for how trials get designed and read. If the MEQ measures a culturally specific, historically contingent religious category rather than a clean psychological or therapeutic mediator, then a trial reporting that MEQ scores predict or correlate with symptom improvement is reporting something less mechanistically clear than it appears. This desk has already tracked adjacent versions of this exact concern from a different angle, the open question of whether psilocybin’s antidepressant effect runs cleanly through the classic hallucinogenic mechanism at all, and a large naturalistic study finding that psychedelics’ famous personality-change effect did not clearly survive rigorous statistical correction outside the clinic. The Saville-Smith and Mosurinjohn paper adds a third, more foundational layer to that pattern: even the instrument used to characterize the experience thought to drive the effect may be measuring a specific, historically loaded construct rather than a neutral psychological variable.

The regulatory stakes

FDA’s newly finalized psychedelic clinical trial guidance devotes real attention to expectancy bias and functional unblinding, precisely because subjective, self-reported measures are the field’s most vulnerable point. A questionnaire whose conceptual foundation is now under direct academic challenge, used as a primary or secondary endpoint in ongoing Phase 2 and Phase 3 programs, is exactly the kind of methodological detail regulators reviewing those endpoints would want to understand. This paper does not allege fraud or data manipulation anywhere in the existing trial record. It alleges something narrower and, in some ways, more consequential for trial design going forward: that a foundational measurement concept was adopted without the scrutiny normally applied to a clinical outcome measure, and that scrutiny is now catching up to it.

The caveats

This is a review and critique, not new clinical data, and it does not reanalyze or invalidate any specific trial’s results. The historical argument about Stace and Pahnke’s original work is a contested scholarly claim; readers with a stake in the underlying religious studies and history of psychology literature may find grounds to contest parts of the genealogy. And a proposed rename, however well argued, requires the field’s actual trial sponsors and regulators to adopt it before it changes anything in practice; nothing about ongoing or completed trials changes today because of this paper’s publication.

The frame

Psychedelic research has spent its current clinical-trial era treating the Mystical Experience Questionnaire as a settled, almost load-bearing piece of infrastructure, the thing that helps explain why a single dose produces effects that outlast the drug’s presence in the body. This paper’s contribution is asking a question that discipline in almost any other clinical field would ask automatically: where did this specific outcome measure actually come from, and does its origin hold up under scrutiny. The proposed answer, rename it and orient it around psychedelic experience broadly rather than a specific mid-century religious category, is a modest, actionable fix rather than a call to throw out decades of data. Whether trial sponsors and the researchers who built their careers on the MEQ take up that fix is a separate question from whether the argument for it is sound, and it is exactly the kind of foundational-assumption scrutiny that has been largely missing from the field’s current methodological conversation.