1. http://www.cancer.gov/cancertopics/coping/feelings/stress-fact-sheet
Can psychological stress cause cancer?
Although stress can cause a number of physical health problems, the evidence that it can cause cancer is weak. Some studies have indicated a link between various psychological factors and an increased risk of developing cancer, but others have not.
Apparent links between psychological stress and cancer could arise in several ways. For example, people under stress may develop certain behaviors, such as smoking, overeating, or drinking alcohol, which increase a person’s risk for cancer. Or someone who has a relative with cancer may have a higher risk for cancer because of a shared inherited risk factor, not because of the stress induced by the family member’s diagnosis.
2. http://www.nimh.nih.gov/health/publications/depression-and-cancer/index.shtml
3. http://www.cancerresearchuk.org/cancer-info/healthyliving/cancercontroversies/stress/ Stress and cancer