Tantra or Yoga. Clinical Studies, Part 3: Comparative Paper

Several clinical studies show how tantric practices and exercises of Vedic traditions—such as Yoga—or Theravada or Mahayana Buddhism have a significant psychobiological impact. This study compares the neurophysiological correlates of practices called tantric and non-tantric meditations through a qualitative systematic review of the collected data. It was evidenced that tantric practices produce increased sympathetic activity, a state of "phasic alertness," and improved performance in visual cognitive tasks. They promote greater wakefulness, reduced propensity for sleep, increased cognitive activity, and metabolic changes contrary to those observed in non-tantric practices due to the relaxation induced by such practices. In contrast, non-tantric practices create a better relaxation response with increased parasympathetic activity and inhibition of the sympathetic system, inducing a hypometabolic state of deep rest where the practitioner remains awake and their attention is in "tonic alertness," accompanied by symptoms corresponding to this hypometabolic state—hypotonia, decreased oxygen consumption, reduced heart rate, and lower blood lactate concentration—changes in normal endocrine function, increased phenylalanine concentration in advanced meditators, elevated plasma prolactin levels, a five-fold increase in plasma arginine vasopressin levels, and a chronic and acute decrease in thyroid-stimulating hormone. This neurophysiological difference corresponds to the differences found in the investigated texts, which indicate that tantric practices aim to increase alertness or an awakened quality of the mind and warn against excessive calm. Conversely, the scriptures and meditation instructions of the Vedic tradition—Yoga, Theravada, or Mahayana—aim to achieve stillness and calmness. We suggest future clinical research from a more interdisciplinary approach, incorporating the theoretical/philosophical framework of the different types of meditation.