Dr. Hans Selye, the father of stress research, mapped the hormonal pathways shown in the illustration above some 40 years ago. Since then, scientists have found that stress provokes a number of even subtler chemical changes in the body that may have profound effects on health, both physical and mental. "There is a constant intertwining of stress systems," says Stanford Neurochemist Jack Barchas. "It's much like a symphony."

Over the past two decades, researchers have learned that stress triggers chemical changes in the brain. Particularly sensitive to emotional strains are the concentrations of potent chemicals called neurotransmitters, which act as messengers between nerve cells. Among these messengers: serotonin, epinephrine (previously called adrenaline), norepinephrine, acetylcholine and dopamine. In a study at Stanford, rats were forced to swim in 4DEGC water for three minutes. Examination of their brain tissue afterward revealed that levels of norepinephrine had fallen 20% and epinephrine 30% to 40%. Scientists also discovered that the body produces its own painkillers, morphine-like chemicals named endorphins. Stress boosts the production of these an algesics, raising the pain threshold. This may explain the mystery of why seriously injured soldiers often feel no pain.

Because stress alters the body's chemical balance, it seems to influence the development of many diseases, including psychiatric disorders. Depression has been associated with low levels of two neurotransmitters, serotonin and norepinephrine. Similarly, schizophrenia seems to be related to an excess of dopamine.

Perhaps the most significant new discovery about stress is its deleterious effect on the immune system. Researchers have discovered that the body's production of its own cancer-fighting cells, including natural killer cells, T-lymphocytes and macrophages, is inhibited by chronic stress.

In late 1981 scientists at the Salk Institute synthesized the remarkable chemical that triggers the body's stress reactions. As illustrated above, the substance, called corticotropin releasing factor (CRF), is produced in the hypothalamus, a tiny but powerful structure sometimes called "the brain's brain." Having duplicated CRF, the Salk scientists now hope to produce a modified version of the chemical that would actually block the body's reaction to stress. This file is automatically generated by a robot program, so viewer discretion is required.