Female spiritist mediums who regularly engage in spirit possession showed mild, short-lived physiological arousal during possession experiences, while nonmedium participants from the same religious context showed relaxation. Compared to controls, mediums had increased heart rate and higher plasma levels of noradrenaline, thyroid-stimulating hormone, prolactin, and creatine phosphokinase during possession. These changes returned to baseline within one hour, with no lasting difference in cardiac autonomic regulation. No group differences were found in melatonin levels. The findings suggest that nonpathological dissociation, unlike pathological dissociation, may involve cognitive control processes and produce only transient physiological changes.
Alleged mediums showed no differences in pineal gland or pituitary volumes, or in urinary 6-sulfatoxymelatonin levels, compared to nonmedium controls. During mediumistic experience, anxiety and heart rate increased to a level between reading and a stressful test, but 6-sulfatoxymelatonin levels did not differ across conditions. Salivary cortisol response to stress was attenuated. The normal neuroimaging and stress reactivity findings contrast with abnormalities typically seen in psychotic and dissociative disorders.