Researchers in Belgium found that that certain psychological factors were associated with infections in the gut after inadvertent exposure to contaminated water. Specifically, anxiety and somatization were associated, but not depression.
This same group of individuals was also at higher risk to develop irritable bowel syndrome (IBS) after this infection. Researchers looked at levels of immune cells and found correlations here that seemed to connect the psychological factors and physical conditions. They called those who developed the IBS symptoms after the gastroenteritis, "post infectious" IBS.
I found the study interesting. It was an unfortunate (contaminated water) natural experiment where those who ended up with both an infectious and later a functional bowel condition had clearly defined psychological factors that increased their risk of these conditions.
The authors concluded that IBS is poorly understood and psychosocial factors are clearly important in its development.
Personality factors have been crucial to understanding chronic pain, TMS, and treatment. Somatization, or tending to express one's emotions physically, or with physical symptoms, seems to be a commonality here.
Announcement of the Newly Published Think Away Your Pain