”Stress” is not a very precise word, but it is a useful word. Certain situations in life are always stressful, such as the death of a spouse or close family member, divorce, separation, illness, loss of a job, or situations such as crowding, noise or temperature changes. Joyful events, such as marriage, pregnancy, or promotion at work, can also be stressors. A certain amount and a certain type of stress is beneficial to health. However, the amount of adverse stress generated by any situation ultimately depends on how the individual “feels” about things. The same stressful event does not mean the same thing to different people, and each person has different coping mechanisms for dealing with stress, which can be more or less effective. How our mind and body react to what we perceive as a stressful event depends on many unique personality factors, which some call “preferential conditioning. When a person feels stressed, there is always a specific psychological response, and the endocrine system becomes active, secreting more types of hormones, including powerful “corticosteroids. The “corticotropin” is the main messenger active in the adrenal glands. It is stimulated to secrete a group of hormones called “corticosteroids” that reduce inflammation in the body, but they also suppress immunity under constant stress. What is the effect of stress in experimental animals? Studies have found that when their adrenal cortex is enlarged, they tend to develop gastric ulcers, and there is shrinkage of the thymus, spleen and lymph nodes, the last three glands being important immune organs. Their slow spreading atrophy under stress is an early sign that there is a close connection between the three systems: neurological, endocrine spear immune. Chronic stress is harmful to our immune system. Natural killer cells and interferons are extremely important for our protection against cancer. Stress can cause our pituitary gland to secrete endorphins, which have a pain-relieving effect. Endorphins can weaken the vitality of a person’s natural killer cells. Harvard researchers examined a group of students and found that those who were “poor copers” (i.e., those who were more anxious or depressed when faced with a problem) had significantly fewer active natural killer cells compared to those who were “good copers”. Studies of mice under stress showed that less interferon was produced. The decrease in interferon may be an effect of catecholamine stress hormones (epinephrine, norepinephrine). When these hormones were given to the animals, a sudden drop in interferon levels was immediately shown. Stress and emotional states can weaken the key components of our defense against cancer (i.e., the viability and number of T cells and natural killer cells, production of interferon). Feelings of “impotence” compromise our immune system and, in animals, make tumors more likely to grow. Depression, loss or separation from loved ones, etc., make our immune system less efficient and lay the initial foundation for a weakened immune defense system.