The Relaxation Response is the physiological state that Herbert Benson, a Harvard cardiologist, identified in the 1970s as the opposite of the fight-or-flight stress response. Triggered by meditation, deep breathing, prayer, or progressive muscle relaxation, the relaxation response produces decreased heart rate, blood pressure, breathing rate, and metabolic rate. Benson's 1975 book 'The Relaxation Response' was the first mainstream Western scientific text to validate meditation as a medical intervention, opening the door to decades of subsequent research. Benson's work was directly informed by Maharishi Mahesh Yogi's Transcendental Meditation.

Reference:

Wikipedia: Relaxation Response

https://en.wikipedia.org/wiki/Relaxation_response