Psychedelic experience dose-dependently modulated by cannabis: results of a prospective online survey

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).


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.”

Authors: Joanna Kuc, Hannes Kettner, Fernando Rosas, David Erritzoe, Eline Haijen, Mendel Kaelen, David J. Nutt & Robin L. Carhart-Harris


A large amount of research is taking place regarding the use of psychedelics as prospective treatments for a range of mental health disorders. The number of clinical trials involving psychedelic’s continues to increase as these compounds have demonstrated both safety and efficacy when used therapeutically.

However, little is known about how psychedelic’s interact with other psychoactive substances. Understanding how drugs interact with one another is an important part of the drug development process as drug-drug interactions can influence the therapeutic outcome and can also lead to unwanted side effects.

Outside of the medical context, psychedelics are often used in tandem with other psychoactive substances. In the present study, researchers explored the subjective effects of psychedelics when used alongside cannabis.

This survey study (n=321) involved participants completing a set of questionnaires including; 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). The online surveys were completed seven days before and one day after a planned experience with a serotonergic psychedelic.

Main findings:

  • The most commonly used psychedelic by the respondents was LSD (50.2%) followed by psilocybin (29.3%).
  • 39% of survey respondents used cannabis alongside psychedelics while one-third of respondents admitted to using cannabis alongside LSD or psilocybin, either often or always.
  • Cannabis use was associated with more intense mystical-type, ego dissolution and visual experiences, and more challenging experiences were associated with higher doses of cannabis.
  • Although the study did not explore the molecular basis of the cannabis-psychedelic interaction, the findings suggest that there is a potential degree of overlap in the receptor targets of psychedelics and cannabis i.e the 5-HT2A receptor.

The authors of the study acknowledge that several limitations exist and thus, cannot definitively state that cannabis had a direct effect on respondents psychedelic experiences. For instance, the doses of the psychedelic or cannabis were not assessed and the time of cannabis consumption was not recorded.

Nonetheless, this study is the first to provide an insight into the effects cannabis has on the psychedelic experience. While the findings are important in terms of harm reduction for recreational drug users, they may eventually be extended to the therapeutic effects of these substances with further research.

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Study details

Compounds studied
LSD Psilocybin

Topics studied

Study characteristics

321 Humans


Authors associated with this publication with profiles on Blossom

Robin Carhart-Harris
Dr. Robin Carhart-Harris is the Founding Director of the Neuroscape Psychedelics Division at UCSF. Previously he led the Psychedelic group at Imperial College London.

David Erritzoe
David Erritzoe is the clinical director of the Centre for Psychedelic Research at Imperial College London. His work focuses on brain imaging (PET/(f)MRI).

Hannes Kettner
Hannes Kettner is a Ph.D. student at the Imperial College Centre for Psychedelic Research and a Scientific Officer at MyDelica. He is interested in studying real-world psychedelic use, including ceremonies, retreats, burns, and what we can learn from them about creating a positive set & setting.

David Nutt
David John Nutt is a great advocate for looking at drugs and their harm objectively and scientifically. This got him dismissed as ACMD (Advisory Council on the Misuse of Drugs) chairman.

Mendel Kaelen
Mendel Kaelen is a neuroscientist and entrepreneur, researching and developing a new category of psychotherapeutic tools for care-seekers and care-providers. Mendel has researched the incomparable effects of music on the brain during LSD-assisted psychotherapy. His work has determined how LSD increases enhanced eyes-closed visual imagery, including imagery of an autobiographical nature. This gives light to how music can be used as another dimension in helping psychotherapists create the ideal setting for their patients.


Institutes associated with this publication

Imperial College London
The Centre for Psychedelic Research studies the action (in the brain) and clinical use of psychedelics, with a focus on depression.

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