One of the major limitations of psychedelic therapy research is the lack of adequate blinding in randomized controlled trials. While many psychedelic therapy trials are placebo-controlled, the active medication (the psychedelic) produces such noticeable and distinct effects that both the participants and the researchers can reliably guess whether a placebo or psychedelic has been administered. This essentially unblinds the study and introduces bias, such as the placebo or expectancy effects, whereby simply believing you received an active medication and expecting a certain outcome influences the observed effects. This could increase the magnitude of the reported effects of the intervention.[1][2]
It’s also important to note that most psychedelic therapy research has been done in populations that are primarily white; there is an overall lack of diversity in terms of ethnicity, culture, and socioeconomic status, which may limit the generalizability of the current research.[1]