The mind and body are not parallel systems occasionally influencing each other but a single integrated organism whose mental and physical dimensions are always in mutual determination. Chronic stress accelerates every major disease process; depression is a significant risk factor for cardiac events; chronic pain reshapes the brain's emotional processing centers. The Sutras never separated the psychological from the physiological: prāṇa flows through both, and intervention at any level of the system ripples through the whole.
Each step builds on the last.