Self-blinding citizen science to explore psychedelic microdosing

[…] Several concerns somewhat dampened our collective enthusiasm:

• Blinding.

o More clarity is needed in the Materials and methods about how participants were blinded and guided to know what a microdose was. This is important to include in the main text. I appreciate the blinding schematics provided by the authors. In addition, a brief description of Citizen Science would be useful in the main text.

We have added a new subsection to the Materials and methods, titled “Self-blinding setup procedure”, which provides a high-level overview of the setup process. This section provides a summary of the procedure for the readers, while further details can be found in the schematic description. The text of this subsection reads as follows:

“A high-level overview of self-blinding is provided here, for a detailed illustration see Figure 2. […] With the QR codes in place, it is possible for the experimenter to recover knowledge of capsule types after randomization without revealing that information to participants.”

Furthermore, we have also added a “Microdose preparation” subsection to the Materials and methods, detailing the directions given to participants. The new section reads:

“Participants were allowed to use any psychedelic substance to microdose with. The microdose dose, i.e. the amount of substance to use as a microdose, was not defined for participants, rather they were instructed to use a microdose dose that they would use outside the study. […] Lastly, this study was not a clinical trial and therefore from a regulatory perspective not allowing for control over and/or directing about drug doses.”

o Please clarify that participants who broke blind did not have their data included, or please clarify why. Also please report the frequency of how many participants broke blind.

Data when participants breaking blind are included in all analysis, in agreement with conventional psychiatric trials that also include such data. We note that blinding is rarely assessed in clinical studies [Baethge, 2013], so examples are limited, nonetheless see [Chen, 2011] or [Rabkin, 1986] for antidepressant studies with guess data. In neither case break blind datapoints are removed from the main analysis, similarly to our study.

As for the break blind rate, we first note that we asked participants to guess their treatment daily (for every day of the dose period). Hence, we can only talk about the % of days when participants break blind (rather than the % of participants) – the same participant could break blind on some days, while not on others. We have updated the subsections “Blind breaking and collection of guess data” (Materials and methods) and “Blinding integrity” (Results) to avoid possible misunderstandings. In particular, now the “Blind breaking and collection of guess data” subsection contains the following sentence:

“In the discussion of our results, the term “break blind” indicates that the participant guessed the capsule correctly for the day (acute outcomes) or week (post-acute outcomes).”

Participants broke blind on 72% of their daily assessments, as it is already reported with details in the “Blinding integrity” subsection in the Results.

• Data availability.

In theory, data is publicly available on their website, but we encountered difficulties accessing it. Please correct this error or address whether it become available upon acceptance of the manuscript.

We checked and the data together with the documentation is publicly available in the data/ folder of the repository we shared. To avoid any misunderstandings, we updated the Transparent reporting document and now a new link is provided, which directly points to the data folder (rather than the repository itself). Furthermore, we removed code that is not relevant to reproducing the results, hoping to make it easier to navigate the codebase. Please let us know if the issue persists.