there is evidence that stress does play a role in blood sugar issues, both diabetes and hypoglycemia.
Many other diseases are affected by stress, as well. I have MS, and when I let myself get really stressed out-- those are the times when I can't walk. Literally can't walk. When I calm down, I'm back to normal. (Which for me is a slight limp.)
This is all the proof I need, personally, of a mind-body connection. It just pays to stay calm, as difficult as that is at times!
Hope this helps!