The emerging science of microdosing: A systematic review of research on low dose psychedelics (1955 – 2021)

A systematic review of 44 studies on microdosing psychedelics, published between 1955 and 2021, found changes in pain perception, time perception, conscious state, and neurophysiology in laboratory studies, and changes in cognitive processing and mental health in self-report studies. The review argues that claims that microdosing effects are largely due to expectancy are premature and possibly wrong. It also provides suggested dose ranges to clarify definitional inconsistencies and offers design suggestions for more rigorous future research.

Study at a glance

Abstract

The use of low doses of psychedelic substances (microdosing) is attracting increasing interest. This systematic review summarises all empirical microdosing research to date, including a set of infrequently cited studies that took place prior to prohibition. Specifically, we reviewed 44 studies published between 1955 and 2021, and summarised reported effects across six categories: mood and mental health; wellbeing and attitude; cognition and creativity; personality; changes in conscious state; and neurobiology and physiology. Studies showed a wide range in risk of bias, depending on design, age, and other study characteristics. Laboratory studies found changes in pain perception, time perception, conscious state, and neurophysiology. Self-report studies found changes in cognitive processing and mental health. We review data related to expectation and placebo effects, but argue that claims that microdosing effects are largely due to expectancy are premature and possibly wrong. In addition, we attempt to clarify definitional inconsistencies in the microdosing literature by providing suggested dose ranges across different substances. Finally, we provide specific design suggestions to facilitate more rigorous future research.