Overwork, lack of sleep, physical illness, excessive alcohol consumption, and smoking are common physi-cal factors that put stress on the body. Some people handle stress well. Others are very negatively influenced by it. Stress creates an excellent breeding ground for illness. Researchers esti-mate that stress contributes to as many as 80 percent of all major illnesses, including cardiovascular disease, cancer, endocrine and metabolic disease, skin disorders, and infectious ailments of all kinds.
Stress is also a common precursor of psychological diffi-culties such as anxiety and depression.
While stress is often viewed as a mental or psychological problem, it has very real physical effects. The body responds to stress with a series of physiological changes that include increased secretion of adrenaline, elevation of blood pressure, acceleration of the heartbeat, and greater tension in the muscles. Digestion slows or stops, fats and sugars are released from stores in the body, cholesterol levels rise, and the composition of the blood changes slightly, making it more prone to clotting. Almost all body functions and organs react to stress. These have the effect of inhibiting the functioning of disease-fighting white blood cells and suppressing the immune response.