Various physiological changes occurring during ecstatic trance have previously been identified in several studies.
Ingrid Mueller (1983) at the University of Munich observed several measures of physiological change that occurred consistently among four volunteer subjects during ecstatic trance using different postures. In her subjects, the blood serum levels of cortisol, epinepherine, and norepinepherine initially increased, then dropped dramatically during the course of the standard fifteen-minute trance, indicating initial stress then relaxation. There was also an increase in beta-endorphins in the blood. Endorphins are a group of proteins that are synthesized in the brain; beta-endorphins are the terminal sequence of 31 amino acids in the polypeptide chain of beta-lipotropin and have a greater analgesic potency than morphine. The presence of beta-endorphins is responsible for the characteristic sense of well-being that accompanies ecstatic trance. The subjects' blood pressure dropped while at the same time pulse rates increased, an unusual and paradoxical condition associated with the preliminary stages of dying. Given this parallel, it is not surprising that shamans often called trance the "little death." Dr. Mueller's findings were consistent regardless of the subject's level of experience with ecstatic trance or the specific posture used.
In a case study (Goodman, 1999) of a woman who was identified as a "trance channel"—that is, an individual who enters an altered state of consciousness to allow a disembodied entity or spirit to communicate through her—as well as a practitioner of ecstatic trance, physiological indices were compared between these two trance states. The findings suggested that during ecstatic trance the changes in blood pressure and pulse dropped during the middle of the trance while during channeling these measures dropped at the end of the trance. The most pronounced difference was observed in the beta-endorphin levels. During ecstatic trance there was a gradual increase that tapered off and remained steady until the end of the experience, while in the channeling trance there was a spike in beta-endorphin levels at the end, reported as an experience of intense rapture. It was evident that these two kinds of altered states of consciousness produced related but not identical physiological conditions.
Using another approach to investigate physiological changes during ecstatic trance, Professor Giselher Guttman at the University of Vienna investigated the cortical DC-potential of subjects, utilizing technology developed for measuring brain wave activity by direct current rather than alternating current as is commonly used in electroencephalograms (Guttman, Goodman, & Korunka, 1990). He reported "a noticeable change of the DC-potential toward negativity in some individuals; those very persons whose subjective rating for the intensity of the trance was higher. The DC-potential for some of the other test persons described an almost perfectly flat, linear course, or even a slight tendency toward positivity." At two electrode sites the trend toward negative DC-shifts was significant at the 10% level. He also found that negative DC-potential was associated with an increase in theta-amplitude among some of the subjects who were more experienced in ecstatic trance. Clearly unusual activity was taking place in the subjects' brains during ecstatic trance, and more experienced subjects showed greater change, although the number of subjects was too small to draw statistically significant conclusions.