The psychedelic effects of cannabis: A review of the literature

Cannabis, especially high-THC varieties, may be able to produce perceptual changes, aversiveness, and mystical experiences similar to those caused by classic psychedelics like psilocybin. Although cannabis is not typically regarded as having psychedelic effects in modern research, historical use alongside psychedelics suggests otherwise. The review finds that recent controlled studies may have failed to observe these effects due to the doses, set, and settings used. Further research is needed to test high doses of THC in therapeutic contexts similar to those used for psychedelics. If cannabis can reliably generate psychedelic experiences, it could be explored as an adjunctive treatment for psychiatric disorders and as an active comparator in clinical trials.

Study at a glance

Abstract

Cannabis and classic psychedelics are controlled substances with emerging evidence of efficacy in the treatment of a variety of psychiatric illnesses. Cannabis has largely not been regarded as having psychedelic effects in contemporary literature, despite many examples of historical use along with classic psychedelics to attain altered states of consciousness. Research into the “psychedelic” effects of cannabis, and delta-9-tetrahydrocannabinol (THC) in particular, could prove helpful for assessing potential therapeutic indications and elucidating the mechanism of action of both cannabis and classic psychedelics. This review aggregates and evaluates the literature assessing the capacity of cannabis to yield the perceptual changes, aversiveness, and mystical experiences more typically associated with classic psychedelics such as psilocybin. This review also provides a brief contrast of neuroimaging findings associated with the acute effects of cannabis and psychedelics. The available evidence suggests that high-THC cannabis may be able to elicit psychedelic effects, but that these effects may not have been observed in recent controlled research studies due to the doses, set, and settings commonly used. Research is needed to investigate the effects of high doses of THC in the context utilized in therapeutic studies of psychedelics aimed to occasion psychedelic and/or therapeutic experiences. If cannabis can reliably generate psychedelic experiences under these conditions, high-THC dose cannabis treatments should be explored as potential adjunctive treatments for psychiatric disorders and be considered as an active comparator in clinical trials involving traditional psychedelic medications.