The Hallucinogen Rating Scale (HRS) was developed by Rick Strassman’s team at the University of New Mexico for its DMT studies. It was drafted from interviews with 19 experienced DMT users and first reported in a 1994 study of 12 volunteers (Strassman et al., 1994). A later analysis describes six domains: somaesthesia (bodily feelings), affect, perception, cognition, volition and intensity (Lawrence et al., 2022).
It has been used well beyond DMT. A Spanish version tested in 75 ayahuasca users and 56 other people found acceptable internal consistency for four of its six scales (Riba et al., 2001). A 2025 analysis pooled 991 HRS questionnaires from 18 publications and 13 substances, and found eight factors rather than six (Calder et al., 2025).
Researchers use the HRS to rate intensity, which is how they approach the community idea of a DMT breakthrough without measuring it directly. Like other self-report scales, it records what people remember, and its best structure is still being refined.
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