To understand what stress does to us, imagine you lived tens of thousands of years ago, at a time when humans were threatened by hungry animals such as saber-toothed tigers and wolves. Our caveman ancestors had to be able to react instantly, either by fighting the beasts or running away.
So humans evolved the ability to respond to a stressful situation instantly, by preparing the body for "fight or flight." Under sudden stress, you will get a burst of exceptional strength and endurance, as your body pumps out stress hormones:
Your heart speeds up
Blood flow to your brain and muscles increases up to 400 percent
Your digestion stops (so it doesn't use up energy that's needed elsewhere)
Your muscle tension increases
You breathe faster, to bring more oxygen to your muscles
Sometimes we can still benefit from this "fight or flight" response - like the case of a mother whose child was pinned under a concrete slab during a tornado. Under stress, she found the strength to lift the huge slab with her bare hands, even though it later took three men to move it.
But much of the time in modern life, the "fight or flight" response won't help. Yet those stress hormones still flood your system, preparing you for physical action. And if you are under stress frequently, it can harm your physical health.
How Stress Can Hurt Us
It has been estimated that two-thirds of all visits to physicians are for stress-related problems. Recent evidence indicates that the physical changes associated with stress may contribute to the leading causes of death - heart disease and cancer.
The effects of stress include the following:
Stress can cause chronic fatigue, digestive upsets, headaches, and back pain.
Stress can affect the blood cells that help you fight off infection, so you are more likely to get colds and other diseases.
Constant stress can increase blood pressure and can increase the risk for stroke.
Stress can increase the danger of heart attacks, particularly if you are often angry and mistrustful.
Stress can make an asthma attack worse.
Stress triggers behaviors that contribute to death and disability, such as smoking, alcoholism, drug abuse, and overeating.
Stress can lead to diminished sexual desire and an inability to achieve orgasm.
Stress makes it harder to take other steps to improve health, such as giving up smoking or making changes in diet.