A systematic review identified nine psychometric instruments used to assess subjective states induced by psychedelic drugs, including the MEQ, 5D-ASC, HRS, PSI, EDI, CEQ, EBI, EDI, and PIQ. Of 857 articles screened, 15 met the criteria. Eight instruments measure phenomenological aspects of the psychedelic experience, and one screens for psychotic or manic episodes. The number of instruments is growing, but many aspects of the psychedelic experience still lack measurement.
After a ban on psychedelic research in the late 1960s, covert studies continued through the 1990s, but the past decade has seen renewed scientific interest in substances such as LSD, ayahuasca, and psilocybin. This chapter reviews EEG and brain imaging studies that evaluate how psychedelics affect the brain. It also examines evidence for using psychedelics as adjunct therapy for psychiatric and addictive disorders, noting that psychedelics appear to have efficacy in treating depression and alcohol-use disorders.