Psychedelics have long been linked to spiritual experiences with a significant majority of participants reporting some form of a spiritual experience often characterized as "universal consciousness" and "connection to all things". These reports are often similar to those of individuals taking part in religious prayers without ingesting any substances.
A recent article by Psychology Today explores the similarities between psychedelics and prayers by highlighting fMRI imaging data from both groups. These images have identified a group of brain structures and cortical regions that become activated and/or demonstrate evidence of active neuroplasticity, with either exposure to a variety of psychedelics or intense spiritual experiences.
The fMRI imaging of the prayer group demonstrates significant changes in the cingulate, frontal, and temporal cortexes of participants after a week-long spiritual retreat. In comparison, the psychedelic group's brain imaging demonstrated acute activation in the exact same three regions of the brain.
The article goes on to conclude that "Taken together, the results of these studies suggest that religious or spiritual experiences and psychedelics increase introspection and a generally positive mood by modulating brain activity in a network of cortical structures that includes the frontal medial and temporal lobes, as well as the cingulate gyrus.
These studies do not prove that these experiences are identical; rather, they suggest that the two experiences involve the activation of overlapping neural structures during intense religious experiences and hallucinations. It should come as no surprise, then, that many cultures have developed strict religious and social rules around the use of plants that produce hallucinations. Extracts from the classical entheogenic psychoactive plants, or symbolic representations of them such as the burning of incense, have often played a significant role in religious ceremonies."