The use of low doses of psychedelic substances (microdosing) is attracting increasing interest. Proponents of microdosing claim a wide range of clinically relevant cognitive enhancement effects. However, ongoing questions around effective doses and the role of expectation have led to confusion and controversy in microdosing science. To help unpack these issues I will present results of a recent systematic review summarising all empirical microdosing research until mid 2021, including a set of infrequently cited studies that took place prior to prohibition. Specifically, we reviewed 44 studies published since 1955, 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. I will discuss methodological issues in microdosing research, and in particular will evaluate recent claims that microdosing may be a placebo effect. I aim to highlight differences between acute and enduring microdosing effects, and provide some specific design suggestions to facilitate more rigorous future research.