Validating and creating a short-form of the persisting effects questionnaire: A measure of positive and negative outcomes from psychedelic experiences.
Abstract
Background
The persisting effects questionnaire (PEQ) is a measure of self-reported positive and negative effects from psychedelic and other experiences. While this measure has been used in many studies on psychedelic substances, the scale has not been formally validated. The PEQ consists of over 140 items as well as several separate single items, causing high participant burden.
Aims
Conduct statistical and qualitative validation procedures for the PEQ and generate a validated short form version (PEQ-SF).
Methods
Validation procedures included (1) conducting exploratory factor analysis for dimensionality reduction, (2) correlations to establish convergent and divergent validity, (3) confirmatory factor analysis in a separate sample, (4) qualitative response process evaluation to ensure items are comprehensible, and (5) comparisons between the original PEQ and the short form in two psychedelic administration studies, one clinical, and one in healthy normals.
Results
We found that the factor structure of the original PEQ was not quantitatively supported; factor analysis revealed a two-factor structure consisting of an overall positive and an overall negative factor. This two-factor structure was maintained in a short form version of the scale, consisting of 14 items with one positive valence and one negative valence factor and three single items from the original PEQ related to well-being and meaning.
Conclusions
We found that the original PEQ did not have adequate validity and created a short form with strong psychometric properties that behaves similarly in drug administration studies.