Your adrenal gland, which is responsible for releasing the stress hormone, becomes weak or sputters out. Then it doesn’t signal properly to help us cope. That, in turn, starts to affect us adversely - not just our biology, but also our emotional response. -- So then you are caught in a vicious cycle of quickly degenerating health because both the stress and the substances are working together to wear down your body systems—your stress axis, your liver, kidney, heart, blood pressure. -- Then you get a double whammy in terms of risk for heart disease and certain types of cancer. Summary of the Mechanism and how it can be induced by intention repetitively to do physical and psychological harm:
see the STRESS AND STRESS MANAGEMENT page.
When we experience something threatening or stressful, two things happen immediately. The first thing is what we call the "fight or flight" arousal response. The whole body is gearing up to move quickly to get out danger. And the second thing is that the body releases the stress hormone cortisol. The body gears up immediately in the face of stressful stimuli. It goes to our energy stores, and releases glucose and insulin so that our muscles have the energy to deal with the stress.
http://thechart.blogs.cnn.com/2011/11/16/the-vicious-physiology-of-stress/
see also: Cushing's syndrome, fight or flight, acid-base imbalance