Chronic Stress may lower the immune system, which defends body against infection and cancer.
Chronic stress due to veriety of situations such as physical illnesses, particularly Psychosomatic illnesses, autoimmune diseases i.e Rheumatoid Arthritis, vascular diseases, Migrain, Collitis and so on can cause change in cellular morphology, that eventually may lead to cancerous cells.
Stress can be a part of our every day life, as a result of not only physical illnesses, but financial issues, relationship problems and environmental exposure to carcinogens can put us at risk for cancer. In order to minimize having the chance of cancer, we need to lower the stress level by minimizing job related stress, working in less stressful and healthy environment, improving relationship by develpoing healthy and positive communication, improving family support, living in "here and now", not to worry too much about the past and or future, as they say, happy people lives in here and now. Taking family vacation from time to time can be very helpful for relaxation, good sleep hygiene i.e going to bed around the same time and waking up from bed around the same time, doing regular exercise and healthy diet can be very helpful.