Differential tolerance to biological and subjective effects of four closely spaced doses of N,N-dimethyltryptamine in humans
Biological Psychiatry May 1, 1996 Rick J. Strassman, Clifford Qualls, Laura M. Berg 129 citations
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Clifford Qualls
Department of Mathematics and Statistics, University of New Mexico, Albuquerque, New Mexico.
2 papers in the library · 134 citations · publishing 1996-2025
Papers
The Hallucinogen Rating Scale: Updated Factor Structure in a Large, Multistudy Sample.
Biological psychiatry global open science March 1, 2025 Abigail E Calder, Clifford Qualls, Gregor Hasler et al. 5 citations
The Hallucinogen Rating Scale (HRS) is a widely used questionnaire for measuring subjective effects of psychedelics and other psychoactive drugs. By analyzing 991 questionnaires from 18 studies involving 13 substances, researchers identified 8 factors with good internal consistency that map onto psychedelic effects. The factor model fit the data better than previous models and showed dose responses for most drugs. Patterns on the 8 factors clearly distinguished classic psychedelics (psilocybin, DMT) from dissociatives (ketamine, salvinorin A), empathogens (MDMA), stimulants (methylphenidate, amphetamine), and THC. The meaningfulness factor uniquely differentiated psychedelics from all other substances, supporting the HRS as a psychometrically sound tool for measuring drug-induced altered states.