Is Microdosing a Placebo?

Claims that microdosing psychedelics works only through placebo effects are premature and possibly wrong, based on eight shortcomings in the existing evidence from dose-controlled studies of low-dose LSD and psilocybin. Only a small number of controlled studies exist, most with small sample sizes. There is some evidence of dose-dependent effects, but only a few doses have been tested, and those may have been too low. Studies have examined only non-clinical populations and have been susceptible to selection bias, while the measured impact of expectancy itself is small. Given these limitations, it is not yet possible to determine whether microdosing is a placebo.

Study at a glance

Abstract

Some recent research and commentary have suggested that most or all the effects reported by people who microdose psychedelics may be explained by expectations or placebo effects. Here we step through all the available evidence from dose-controlled studies that have investigated the effects of low doses of LSD and psilocybin. We suggest eight reasons why current claims that microdosing is predominately a placebo are premature and possibly wrong: 1) there have been only a small number of controlled studies; 2) studies have had small sample sizes; 3) there is evidence of dose-dependent effects; 4) studies have only investigated the effects of a small number of doses; 5) the doses investigated may have been too small; 6) studies have looked only at non-clinical populations; 7) studies so far have been susceptible to selection bias; and 8) the measured impact of expectancy is small. Considering the available evidence, we conclude that it is not yet possible to determine whether microdosing is a placebo.