Scientists have known for some time that stress can aggravate physical or mental illnesses. We also know that stress is also associated with an increased risk for such mental and physical illnesses such as:

Depression
Irritable Bowel Syndrome (IBS)
Breast Cancer
Headache
During the normal stress response, the nervous system and endocrine systems respond. Chronic stress can result in continued response of these systems, especially in regard to hormone release, which can impact other body systems.