Stress: It's Worse Than You Think

Stress affects your brain and body. Too much of it can have a fatal effect. Here's what you can do to relax.

By John Carpi, published on January 01, 1996 - last reviewed on June 22, 2006

The problem is, what we call the stress system is actually responsible for coordinating much more than just our response to stress. "Initiating a response to stress is just one of many things the system controls," says Jean King. "These hormones are carefully regulated substances that direct everything from the immune system to the cardiovascular system to our behavioral system."

For example, cortisol directly impacts storage of short-term memory in the hippocampus. The stress hormones dopamine and epinephrine are also neurotransmitters widely active in enabling communication among brain cells. Directly and indirectly, they act on numerous neural networks in the brain and throw off levels of other neurotransmitters. Stress, it's now known, alters serotonin pathways. And through effects on serotonin, stress is now linked with depression on one hand, aggression on the other.

The developing picture of the biochemistry of stress in some ways takes the heat off psychology. "We used to say that physical manifestations of stress were psychological defense mechanisms employed as a way to shield the person from revisiting a particularly troubling event in their past," says Roosevelt's Smith. "What is far more likely is that the same chemicals being released in response to stress are triggering physical reactions throughout the body."

A torrent of studies catalogue how even a little stress can have wide-ranging effects on the body. Researchers have found that:

Epinephrine, released by the adrenal glands in response to stress, instigates potentially damaging changes in blood cells. Epinephrine triggers blood platelets, the cells responsible for repairing blood vessels, to secrete large quantities of a substance called ATP. In large amounts, ATP can trigger a heart attack or stroke by causing blood vessels to rapidly narrow, thus cutting off blood flow, says Thomas Pickering, M.D., a cardiologist at the New York Hospital-Cornell Medical Center.
Other substances released in the stress response impair the body's ability to fight infections. In one study, researchers tracked the neurohormones of parachute jumpers. They found an 84 percent surge in nerve growth factor (NGF) among young Italian soldiers attempting their first jump, compared with nonjumpers. Up to six hours after they hit ground, the jumpers' NGF levels were 107 percent higher than in nonjumping soldiers. Released by the pituitary gland as part of the stress response, NGF is attracted like a magnet to disease-fighting cells, where it hinders their ability to ward off infections. An immune system thus suppressed can raise susceptibility to colds—or raise the risk of cancer.
Cortisol activation can similarly damage the immune system. Sheldon Cohen, Ph.D., professor of psychology at Carnegie Mellon University, gave 400 people a questionnaire designed to quantify the amount of stress they were under. He then exposed them to nose drops containing cold viruses. About 90 percent of the stressed subjects (versus 74 percent of those not under stress) caught a cold. He found they had elevated levels of corticotrophin-releasing factor (CRF). "We know that CRF interferes with the immune system," Cohen says. "That is likely the physical explanation why people under stress are more likely to catch a cold."
Stress hormones are also implicated in rheumatoid arthritis. The hormone prolactin, released by the pituitary gland in response to stress, triggers cells that cause swelling in joints. In a study of 100 people with rheumatoid arthritis, Kathleen S. Matt, Ph.D., and colleagues at Arizona State University found that levels of prolactin were twice as high among those reporting high degrees of interpersonal stress than among those not stressed. Other studies have shown that prolactin migrates to joints, where it initiates a cascade of events leading to swelling, pain, tenderness. "This is clearly what people mean when they say stress is worsening their arthritis," Matt says. "Here we have the hormone released during stress implicated in the very thing that causes arthritis pain, swollen joints."
After being released by the pituitary gland, the stress hormone ACTH can impede production of the body's natural pain relievers, endorphins, leading to a general feeling of discomfort and heightened pain after injury. High levels of ACTH also trigger excess serotonin, now linked to bursts of violent behavior.

By charting the pathways stress hormones take throughout the body, biological cartographers are doing more than mapping the links between stress and disease. Having caught cascades of biochemicals in flagrante delicto, researchers are diagramming the exact lines of communication between mind and body. Ultimately, they will force us to erase the dividing line between what is biological and what is psychological.

Important as they are, elucidating the neurohormones released during stress and relating them to body systems is not even the whole story. If that were all there was to how stress works, you would expect any physical reaction to occur immediately, since these hormones typically remain elevated for only a short time. And you would expect everyone to show some physical reaction. Certainly, not all people suffer a heart attack or asthma attack when they get upset. Some seem able to take stress in their stride, while others routinely are hobbled.