When people expected microdosing to help, it did — a study that points to a strong placebo effect
A 2021 study followed 81 adults who were planning to start microdosing psychedelics on their own, tracking their mental health weekly for four weeks and measuring how much they expected to improve before they began.
This study followed 81 adults who were planning to start microdosing classic psychedelics on their own, tracking their mental health each week for four weeks. Over that time, their well-being and emotional stability rose and their anxiety and depression eased. But the study also measured how much people expected to improve before they began — and those higher expectations predicted bigger improvements. The authors describe this as suggestive of a significant placebo response, and caution against reading the results as proof that microdosing itself caused the change. There was no comparison group taking a dummy pill, so cause and effect can't be separated here.
This prospective, naturalistic observational study (n = 81 completers, from 253 who completed baseline measures) tracked adults planning to begin a weekly microdosing regimen of classic psychedelics, with web-based self-report at baseline and weekly across a four-week test period. Self-reported psychological well-being and emotional stability increased and state anxiety and depressive symptoms decreased over the period (time effects: well-being ηp² = 0.18, depression ηp² = 0.31, anxiety ηp² = 0.24). Critically, participants' positive expectancy at baseline predicted their subsequent improvement in well-being, which the authors describe as suggestive of a significant placebo response, cautioning against zealous inferences about microdosing's therapeutic value.
The authors state the central limitations plainly: there was no control or placebo group, so the changes cannot be attributed to microdosing itself over and above expectation or placebo; spontaneous remission and regression to the mean cannot be excluded; and high attrition (a 68% dropout by the four-week endpoint) may have biased the sample toward those who felt benefit. As a naturalistic study, participants used substances and doses of their own choosing rather than a fixed, controlled dose, and reported on themselves online. The finding that baseline expectancy predicted outcomes is the study's most durable contribution — an empirical basis for reading much of microdosing's reported benefit as a placebo response.
Participants' positive expectancy scores at baseline predicted subsequent improvements in well-being, which the authors describe as suggestive of a significant placebo response (Kaertner et al., 2021).
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