Psychedelic experience dose-dependently modulated by cannabis: results of a prospective online survey
Carhart-Harris, R. L., Erritzoe, D., Haijen, E., Kaelen, M., Kettner, H., Kuc, J., Nutt, D. J., Rosas, F. E.
This survey study (n=321) explored the subjective effects of psychedelics when used alongside cannabis. It was found that the use of cannabis alongside classic serotonergic psychedelics such as LSD and psilocybin led to a more intense psychedelic experience across a number of measures including; the Mystical Experience Questionnaire (MEQ) and the Ego Dissolution Inventory (EDI).
Abstract
Rationale: Classic psychedelics are currently being studied as novel treatments for a range of psychiatric disorders. However, research on how psychedelics interact with other psychoactive substances remains scarce.Objectives: The current study aimed to explore the subjective effects of psychedelics when used alongside cannabis.Methods: Participants (n = 321) completed a set of online surveys at 2 time points: 7 days before, and 1 day after a planned experience with a serotonergic psychedelic. The collected data included demographics, environmental factors (so-called setting) and five validated questionnaires: Mystical Experience Questionnaire (MEQ), visual subscales of Altered States of Consciousness Questionnaire (ASC-Vis), Challenging Experience Questionnaire (CEQ), Ego Dissolution Inventory (EDI) and Emotional Breakthrough Inventory (EBI). Participants were grouped according to whether they had reported using no cannabis (n = 195) or low (n = 53), medium (n = 45) or high (n = 28) dose, directly concomitant with the psychedelic. Multivariate analysis of covariance (MANCOVA) and contrasts was used to analyse differences in subjective effects between groups while controlling for potential confounding contextual ‘setting’ variables.Results: The simultaneous use of cannabis together with classic serotonergic psychedelics was associated with more intense psychedelic experience across a range of measures: a linear relationship was found between dose and MEQ, ASC-Vis and EDI scores, while a quadratic relationship was found for CEQ scores. No relationship was found between the dose of cannabis and the EBI.Conclusions: Results imply a possible interaction between the cannabis and psychedelic on acute subjective experiences; however, design limitations hamper our ability to draw firm inferences on directions of causality and the clinical implications of any such interactions.