Thank you Sandy for starting this thread, and everybody else who has posted too.
Hopeful thank you for the interesting links, which I will have to try and find time to read in full.
This is a huge subject and I restrict myself to the biology and chemistry of it all albeit at my very low level of understanding.
From what I have read I think it is clear that there is no question of a link between stress and illness. It is a bit of a chicken and egg I suspect in terms of which comes first. It would seem reasonable that they in a sense developed in tandem with one driving the other.
By way of example at the extremes, please find below and abstract of a trial on post traumatic stress disorder. Once you accept that there is a medical impact of stress at this level, it would be reasonable to assume that much lower levels of stress have an impact too.
The ability to deal with stress is to some extent diet linked. As often posted there is significant evidence that balancing the omega threes and sixes and will reduce the production of inflammatory factors in the body. Inflammatory factors link to the immune system. The diseases listed below are generally regarded as inflammatory (I am uncertain about a thyroid disease) Omega threes and sixes play big roles in brain and body function at a number of levels. If your body is less prone to inflammatory factors then on the balance of probabilities it will be less reactive in stressful situations.
Posttraumatic stress disorder and physical illness: results from clinical and epidemiologic studies.
http://www.ncbi.nlm.nih.gov/sites/en...RVAbstractPlus
"To test this hypothesis, we assessed the association between chronic PTSD in a national sample of 2,490 Vietnam veterans and
the prevalence of common autoimmune diseases, including rheumatoid arthritis, psoriasis, insulin-dependent diabetes, and thyroid disease. Our analyses suggest that chronic PTSD, particularly comorbid PTSD or complex PTSD, is associated with all of these conditions. In addition, veterans with comorbid PTSD were more likely to have clinically higher T-cell counts, hyperreactive immune responses on standardized delayed cutaneous hypersensitivity tests, clinically higher immunoglobulin-M levels, and clinically lower dehydroepiandrosterone levels.
The latter clinical evidence confirms the presence of biological markers consistent with a broad range of inflammatory disorders, including both cardiovascular and autoimmune diseases."