Benefits of Psychedelics’ Microdosing May Be Explained by Placebo Effect Interview with:|
Balázs Szigeti, PhD
Center for Psychedelic Research
Imperial College London  What is the background for this study?  What are the main findings?

Response: The study investigated microdosing which is the regular intake of small doses of psychedelics drugs (e.g. LSD; a typical microdose is about 10-20% of recreational doses).  This study used a ‘self-blinding’ citizen science methodology, where participants, who microdosed on their own initiative using their own substance could participate online. Participants were given online instructions on how to incorporate placebo control into their microdosing routine without clinical supervision. The strength of this design is that it allowed us to obtain a large sample size while implementing placebo control at minimal logistic and economic costs.  The study was completed by 191 participants, making it the largest placebo-controlled trial on psychedelics to-date, for a fraction of a cost of a clinical study. What should readers take away from your report?

Response: We found that after 4 weeks of microdosing, all psychological parameters measured (well-being, mindfulness, life-satisfaction, paranoia) improved statistically significantly. However, participants in the placebo group improved similarly and there was no between group differences in any outcome. We found no evidence for change in cognitive performance either in the placebo or the microdose group.

Acute (emotional state, drug intensity, mood, energy, and creativity) and post-acute (anxiety) scales showed small, but significant microdose vs. placebo differences (Cohen;s D < 0.3), however, these results can be explained by participants breaking blind. Specifically, when we considered data from participants who could not accurately guess their drug condition, the small microdose-placebo difference disappeared on all scales except the drug intensity visual analogue scale. This finding suggest that increased drug intensity is the only true drug effect, which could explain how participants were breaking blind. What recommendations do you have for future research as a result of this work?

Response: It is crucial to emphasize that our data clearly shows the benefits of microdosing, however, the same benefits are reproduced by participants taking placebos. Therefore, our conclusion is that the anecdotal reports about the benefits of microdosing are valid, however, the mechanism behind those improvements is not  pharmacological, but rather explained by placebo-like expectation effects. Our results about microdosing are negative, but they can be looked at as a positive result about the importance of placebo-like expectation effects. 

Furthermore, we show for the first time that it is possible to incorporate placebo control into citizen science projects with our ‘self-blinding methodology’. We are actively looking to collaborate with researchers from other domains to develop new self-blinding citizen science initiatives. Is there anything else you would like to add?

Response: Given this demonstration of the importance of psychological expectations, I think the research community should do more to assess blinding integrity during trials. It is one thing to have a formal placebo control group in a study, but it is a separate question whether the study is functionally blinded as well. Unfortunately, the vast majority of clinical trials still does not assess and report blinding efficacy and even more rarely it is considered during analysis.


Balázs Szigeti, Laura Kartner, Allan Blemings, Fernando Rosas, Amanda Feilding, David J Nutt, Robin L Carhart-Harris, David Erritzoe. Self-blinding citizen science to explore psychedelic microdosing. eLife, 2021; 10 DOI: 10.7554/eLife.62878

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Last Updated on March 4, 2021 by