In a self-blinding study, people who already plan to use a substance follow instructions to create their own placebo control. They prepare identical-looking capsules, some without the substance, and arrange them so that they don’t know which they take on a given day. Researchers then compare outcomes on active and placebo days without running a clinic.
The best-known example is a 2021 Imperial College London microdosing study. Of the 191 people who completed it, both the microdose and placebo groups improved over four weeks, with no significant differences between them on psychological outcomes (Szigeti et al., 2021). Its authors noted that small acute differences could be explained by participants breaking blind (Szigeti et al., 2021).
The design is cheap and reaches people in their real routines, but nothing is verified: substance, purity and amount were not checked, and only 23% of participants used psilocybin mushrooms (Szigeti et al., 2021). It shows how much expectancy can explain, without settling what microdosing does.
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