American Medical Association Family Medical Guide - American Medical Association [48]
The most harmful kind of stress is chronic stress—uncontrollable stress that continues with no end in sight. Having a demanding job, caring for a loved one with Alzheimer’s disease, or living in extreme poverty are common sources of chronic stress. Long-term situations that are unpredictable, such as living with an abusive spouse, can also produce chronic stress. Traumatic events such as rape, a natural disaster, or military combat can cause a severe psychological disturbance called posttraumatic stress disorder (see page 720).
Chronic stress generates feelings of helplessness and hopelessness that can lead to major depression (see page 709). Constant stress can cause many other health problems, including irritable bowel syndrome (see page 765), high blood pressure, heart disease, and infertility (see page 493). Learning how to handle the stress in your life can help keep your mind and body healthy.
How Your Body Responds to Stress
The human body is designed to cope with sudden, short-term threats. Early humans had to fight for food and shelter and deal with attacks from predators to survive. Their bodies responded to an immediate threat by energizing them and sharpening their attention so they could either stand and fight or escape the danger (called the fight-or-flight response). Today your body responds in the same way—not only to a threat, but also to other pressures such as demands from your employer, children, and family.
When you face a potential threat, your emotions and senses alert a small center in your brain called the hypothalamus. The hypothalamus signals the pituitary gland in the brain and the adrenal glands (two small glands that sit on top of the kidneys) to release a number of different hormones. These hormones work together with your autonomic nervous system, the part of the nervous system that controls involuntary activities of your body such as breathing and heart rate, to prepare your body to respond to the threat.
Cortisol is one of the most important hormones the body releases in response to stress. Cortisol performs a number of functions in the body, but during stress it pumps glucose (sugar) into the bloodstream to fuel the body for action. It also temporarily suppresses some systems of the body that are not critical to the fight-or-flight response, such as the immune system. (See page 13 to learn how the actions of cortisol during chronic stress can adversely affect your health.)
At the same time, your body releases the hormone adrenaline (epinephrine), causing heart rate and breathing to increase, the airways and the blood vessels in the muscles to widen, and the pupils in the eyes to dilate (widen). Blood flows to the brain and muscles, where energy is needed most. Body processes that are not required for the threat response—such as digestion, growth, reproduction, and the immune response—shut down temporarily. Now your body is ready to face or retreat from the challenge.
Once the stressful event is over, your body returns to normal. Your pupils contract, your heart rate and breathing slow, and digestion proceeds as usual. Because the stress response was designed primarily as a survival mechanism, it activates easily but takes a long time to shut down, and you may need to make a conscious effort to bring your body back into equilibrium. Your nervous system triggers the relaxation response. Harnessing this power consciously can help you better handle the stress in your life (see page 59).
Each person’s response to stress differs, influenced by a combination of such factors as heredity; childhood experiences; personality; diet, exercise, and sleep habits; having or not having close personal relationships; and income level and social status. Some people seem less able to cope with life