Here's a hearty endorsement of the National Geographic special on stress. They examine with a pre-eminent neuro-biologist the real physical dangers stress causes on the body down to the chromosome level.
Here's a quiz from National geographic site, and a pointer to the very informative site at Stanford about the documentary.
In a quick laymen's synopsis: stress has real measurable effects on multiple systems in the body including immune function, brain, diabetes, cardiovascular system even a protective layer on the chromosomes called telomeres. So your genes will ultimately unravel themselves if these telomeres decay. Well they decay faster (essentially all your body's cells age faster) under stress!
In other examples, obesity is not only exacerbated by stress, it may be a root cause. There are even lifetime effects of stress in utero - you come away realizing that unresolved and untreated stress is very dangerous, particularly over time to the body.
This was all backed up by studies they did on baboons with brain scans, examining various systems, even looking increased viseral fat (the worst kind, that causes heart attacks). It was all tracked back to stress.
On the positive side, when social interactions and stress reduction took place, the effects to telomeres and other systems in the body were reversed! So there is hope for positive measures.
Some of the conclusions: we need to value and promote a society that considers stress reduction as a major goal because it makes people flourish.
I was babysitting for my wife last night and didn't get to workout until relatively late. But I thought - what better night for Yoga-X. And for sure, although I ended near 11, I showered and slept like a baby last night!
So exercise and use your relaxation techniques - your whole being (body and mind) will experience reduced stress and aging because of it!