The Measurement Problem
Twelve dimensions, and the problem of measuring them
The dimensions above are what our research sets out to understand. There is an awkward problem with that: we have not identified a common instrument that measures them together over time. This is the least glamorous gap in psychedelic science, and we think it is the most important one.
Background reading: Psychedelics and human development.
A 2024 systematic review in the Journal of Psychopharmacology examined 93 clinical trials of classic psychedelics and found 17 different rating scales in use across them. Its authors called for the field to develop a core outcome set, a common minimum that every study reports, and recommended that instruments be designed to assess the setting of an experience. We have not identified either in use.
There is a second gap underneath the first. Nearly every validated instrument in the field measures the acute experience: what happened during the hours the substance was active. Very little measures what a person was actually seeking, or whether they found it, a month or a year later. For a field increasingly asked to justify itself with durable outcomes, that is a strange place to be.
The consequence shows up plainly in the research. In what its authors describe as the largest prospective study of naturalistic psilocybin use published to date, participants most often named self-exploration, and most named several reasons at once, mental health and therapy among them. Their outcomes were reported on measures of anxiety, depression, alcohol misuse, cognitive flexibility, emotion regulation, spiritual wellbeing, extraversion, neuroticism, and burnout. The purpose a person recorded and the instrument that measured the outcome came from different frames. That same study found that, of those who completed each follow-up, 11% at two to four weeks and 7% at two to three months reported persisting negative effects, and we have not identified a standard for how such an effect should be defined, timed, or recorded.
So results cannot be pooled across studies, benefits cannot be compared, and harms cannot be counted properly. Every new dataset arrives in its own dialect.
What we are building
Three pieces, all of them plumbing rather than headline science:
- A minimum common data element set, the short list of facts any record of a psychedelic experience should carry to be comparable with any other: substance and whether its identity was verified, preparation form, quantity with units and route, setting and supervision, screening performed, medications, and what followed, at fixed intervals.
- An outcome measure referenced to purpose, built on the twelve dimensions above, and anchored to what the person recorded before the experience rather than what they remember afterwards. Purpose recorded in advance is a fixed reference point. Purpose recalled later tends to be revised in light of how things turned out.
- A standard case definition for persisting adverse effects, with fixed observation windows, so that the persisting-effects finding above becomes a number that can be checked, compared, and either confirmed or corrected.
All of it will be published openly and free of charge, with no licence fee and no restriction on use, for researchers, state programmes, registries, and clinicians to adopt or adapt. The first piece is out: version 1.1 of the minimum common data element set, 23 elements in six groups with a proposed case definition for persisting adverse effects, is open for public comment until 2 December 2026. The outcome measure is still in development.
A word on what this is not. We are not claiming to be an authority, and a measure is not made legitimate by being announced. It earns its place by being used, tested, and criticised until either it survives or something better replaces it. So we publish drafts rather than verdicts, we invite people to take them apart, and we will say plainly where we got it wrong. Metanoia is well suited to this particular job for one structural reason: we sell nothing to the people our research informs, so no finding is worth more to us than any other.