Stress
Stress can cause headaches, high blood pressure, insomnia and, yes, tummy trouble. Depression has been linked with digestive problems (including loss of appetite and weight loss) as well as irritable bowel disease.
The relationship seems to go both ways, according to a study published in 2012 in the journal Gut. In other words, depression may be causing the stomach aches but constant abdominal pain may just as easily lead to depression and anxiety.
