I'm having some trouble posting, but I think I found an answer for you. I downloaded the preview of the following book after seeing it in this site's book referral list. This is what I found:
The Relaxation and Stress Reduction Workbook, by Elizabeth Robbins Eshelman, et al; Chapter 1, How You React to Stress
"Regrettably, during times of chronic stress when the fight-or-flight physiological responses continue unchecked, something else happens that can have long-term negative effects. The adrenal glands secrete corticoids (adrenalin, epinephrine or norepinephrine), which inhibit digestion, reproduction, growth, tissue repair...
"Chronic or persistent stress can occur when life stressors are unrelenting...
"There are also some indications that the continued release and depletion of norepinephrine during a state of chronic stress can contribute to depression and anxiety."