Microdosing with psilocybin mushrooms: a double-blind placebo-controlled study

A double-blind placebo-controlled trial tested the effects of a low (0.5 g) dose of dried psilocybin mushrooms on 34 individuals beginning a microdosing protocol. The active dose produced more intense acute subjective effects than placebo, but only among participants who correctly guessed their condition. These effects coincided with reduced EEG theta-band power and preserved Lempel-Ziv broadband signal complexity. No evidence was found for enhanced well-being, creativity, or cognitive function; instead, small changes toward cognitive impairment appeared. The findings suggest that expectation, not the drug itself, accounts for many anecdotal benefits attributed to psilocybin microdosing.

Study at a glance

Abstract

Abstract The use of low sub-perceptual doses of psychedelics (“microdosing”) has gained popularity in recent years. Although anecdotal reports claim multiple benefits associated with this practice, the lack of placebo-controlled studies severely limits our knowledge of microdosing and its effects. Moreover, research conducted in standard laboratory settings could fail to capture the motivation of individuals engaged or planning to engage in microdosing protocols, thus underestimating the likelihood of positive effects on creativity and cognitive function. We recruited 34 individuals starting to microdose with psilocybin mushrooms ( Psilocybe cubensis ), one of the materials most frequently used for this purpose. Following a double-blind placebo-controlled experimental design, we investigated the acute and short-term effects of 0.5 g of dried mushrooms on subjective experience, behavior, creativity (divergent and convergent thinking), perception, cognition, and brain activity. The reported acute effects were significantly more intense for the active dose compared to the placebo, but only for participants who correctly identified their experimental condition. These changes were accompanied by reduced EEG power in the theta band, together with preserved levels of Lempel-Ziv broadband signal complexity. For all other measurements there was no effect of microdosing except for few small changes towards cognitive impairment. According to our findings, low doses of psilocybin mushrooms can result in noticeable subjective effects and altered EEG rhythms, but without evidence to support enhanced well-being, creativity and cognitive function. We conclude that expectation underlies at least some of the anecdotal benefits attributed to microdosing with psilocybin mushrooms.