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Psychological stress doesn't just put your head in a vise. New studies document exactly how it tears away at every body system--including your brain. But get this: The experience of stress in the past magnifies your reactivity to stress in the future. So take a nice deep breath and find a stress-stopping routine this instant.
Technological advances have expanded the business day. Leisure time has shrunk. Bathing-suited business men walk beaches on Sundays with cellular phones stuck to their ears, planning the next morning's meetings. Laptop computers find their way on vacations. The family icons of today are working couples picking up their children on their way home to dinners prepared by caterers or fast food chefs. Grieving time has shrunk. The divorce rate hovers near its highest in history. The concept of job security has gone the way of the dirigible. Yet there is no time to pick up the pieces. "Just snap out of it," yells the therapist as he slaps his patient in a newspaper cartoon. The caption: Time-saving single-visit psychotherapy.
Stress has become so endemic it is worn like a badge of courage. The business of stress reduction, from workshops to relaxation tapes to light and sound headsets, is booming. If ours is a culture without deep intimacy, then our relationship with stress is the exception.
Yet not even this familiarity can cushion the findings of research: The effects of stress are even more profound than imagined. It penetrates to the core of our being. Stress is not something that just grips us and, with time or effort, then lets go. It changes us in the process. It alters our bodies--and our brains.
Stress sensitization is uncharitably subversive. While the chemical signaling systems of body and brain are running amok in a person sensitized to stress, that person's perception of stress remains unchanged. It's as if the brain, aware that the burner on the stove is cool, still signals the body to jerk its hand away. "What happens is that sensitization leads the brain to re-circuit itself in response to stress," says psychologist Michael Meaney, Ph.D., of McGill University. "We know that what we are encountering may be a normal, everyday episode of stress, but the brain is signaling the body to respond inappropriately." We may not think we are getting worked up over running late for an appointment, but our brain is treating it as though our life were on the line.
Because some stress is absolutely necessary in living creatures, everyone has a built-in gauge that controls our reaction to it. It's a kind of biological thermostat that keeps the body from launching an all-out response literally over spilled milk. Sensitization, however, lowers the thermostat's set point, says psychologist Jonathan C. Smith, Ph.D., founder and director of the Stress Institute at Roosevelt University in Chicago. As a result, the body response typically reserved for life-threatening events is turned on by life's mundane aggravations. In this hothouse of hyperreactivity, bio-chemicals unleashed by stress may boil over at the most trivial of events, like our missing a train or being shunted to voice mail.
"Years of research has told us that people do become sensitized to stress and that this sensitization actually alters physical patterns in the brain," says Seymour Levine, Ph.D., of the University of Delaware. "That means that once sensitized, the body just does not respond to stress the same way in the future. We may produce too many excitatory chemicals or too few calming ones; either way we are responding inappropriately."
The revelation that stress itself alters our ability to cope with stress has produced yet another remarkable finding: Sensitization to stress may occur before we are old enough to prevent it ourselves. New studies suggest that animals from rodents to monkeys to humans may experience still undetermined developmental periods during which exposure to stress is more damaging than in later years. "For example, we have known that losing a parent when you are young is harder to get over than if your parent dies when you are an adult," says Jean King, Ph.D., of the University of Massachusetts Medical School. "What we now believe is that a stress of that magnitude occurring when you are young may permanently rewire the brain's circuitry, throwing the system askew and leaving it less able to handle normal, everyday stress."
It is the stew of chemicals released by such provocations that ultimately explains the noose stress ties between mind and body. "This new paradigm of stress demonstrates that there is a link between psychological events and physical eruptions, between mind and body," King says. "The psychological events that are most deleterious probably occur during infancy and childhood--an unstable home environment, living with an alcoholic parent, or any other number of extended crises." The new paradigm also firmly ties everyday psychological stress to such suspect complaints as ulcers, headaches, and fatigue.
Whether we end up stressed-out executives or laid-back surfers, we all start out with the same biological machinery for responding to stress. Stress activates primitive regions of the brain, the same areas that control eating, aggression, and immune response. It switches on nerve circuits that ignite the body's fight-or-flight response as if there were a life-threatening danger.
From this evidence researchers have concluded that the stress response is "wired" into the brain, that we inherit the same ancient reactions that jump-started hunter-gatherers to escape a charging saber-tooth tiger without having to give their actions time-consuming thought. Only this same life-or-death reaction is now called into play largely by non-life-threatening situations. Studies have found the same fight-or-flight circuits all working overtime in response to such varied stressors as extreme exercise, the death of a loved one, an approaching deadline.
One conclusion from the evidence is that we may be victims of evolution, hard-wired with a stress response system that's better suited to a life filled with occasional life-threatening events than one filled with everyday irritations like failing a test or blowing a sales call. Unfortunately, when stresses become routine, the constant biochemical pounding takes its toll on the body; the system starts to wear out at an accelerated rate.
By responding to the stress of everyday life with the same surge of biochemicals released during major threats, the body is slowly killing itself. The biochemical onslaught chips away at the immune system, opening the way to cancer, infection, and disease. Hormones unleashed by stress eat at the digestive tract and lungs, promoting ulcers and asthma. Or they may weaken the heart, leading to strokes and heart disease. "Chronic stress is like slow poison," King observes. "It is a fact of modern life that even people who are not sensitized to stress are adversely affected by everything that can go wrong in the day."
If stress has a central command post, it is the hypothalamus, a primitive area of the brain located near where the spine runs into the skull. By way of a dazzling array of hormonal signals, the hypothalamus is closely connected with the nearby pituitary gland and the distant adrenal glands, perched atop the kidneys. The so-called hypothalamicpituitary axis (HPA) has a virtual monopoly on basic body functions. It regulates blood pressure, heart rate, body temperature, sleep patterns, hunger and thirst, and reproductive functions, among many other activities.
About the size of a grape, the hypothalamus does its work by releasing two types of signaling hormones; those that stimulate glands to release other hormones and those that inhibit the glands from performing their job. Among the best known of these hormones are follicle-stimulating and luteinizing hormones, which, dispatched on a strict schedule from the pituitary, begin the monthly process that prepares women for pregnancy or menstruation.
Like a cherry attached by its stem, the pituitary gland hangs off the hypothalamus waiting to receive instructions on which of its many hormones to release and in what quantity. In hormonal terms it is the little gland that could. The pituitary releases substances that regulate growth, sex, skin color, bone length, and muscle strength. It also releases adrenocorticotropin, a hormone that activates the third part of the body's stress system, the adrenal glands.
When stress sets off the usual ferocious communication between the hypothalamus and the pituitary, the buck stops at the adrenal glands. They manufacture and release the true stress hormones--dopamine, epinephrine (also known as adrenaline), norepinephrine (noradrenaline), and especially cortisol. So responsive to the adrenal hormones are basic body functions like blood flow and breathing that even minute changes in levels of these substances can significantly affect health.
Slight overproduction of dopamine can constrict blood vessels and raise blood pressure; a shift in epinephrine could precipitate diabetes, or asthma, by constricting tiny airways in the lungs. If the adrenal gland slacks off on cortisol production the result may be obesity, heart disease, or osteoporosis; too much of the hormone can cause women to take on masculine traits like hair growth and muscle development and lead to one of the greatest fears of all for aging men--baldness. High levels of cortisol also may kill off brain cells crucial for memory.
The adrenal gland is also home of the grand daddy of all stress reactions, the fight-or-flight response. Sensing impending danger the hypothalamus presses out cortisol-releasing factor, a hormone that prompts the pituitary gland to release adrenocorticotropin (ACTH). Carried in the bloodstream to the adrenal glands, ACTH triggers production of cortisol and epinephrine. The end result of this hormonal relay is a sudden surge in blood sugar, heart rate, and blood pressure--everything the body needs to flee or confront the imminent danger.
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."
Researchers have found that even a little stress can have wide-ranging effects on the body:
- 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 (CRY). "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."
o 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.
Lawrence Brass, M.D., associate professor of neurology at Yale Medical School, found that severe stress is one of the most potent risk factors for stroke more so than high blood pressure--even 50 years after the initial trauma. Brass studied 556 veterans of World War II and found that the rate of stroke among those who had been prisoners of war was eight times higher than among those veterans who had not been captured.
The findings at first confused Brass. After all, the stress hormones that cause heart disease and stroke are elevated only for a few hours after a stressful event. "I began to realize we would have to take our understanding of stress farther when I began to see that in some people stress can cause disease years after the initial event," he says. He concluded that the immediate effect of the war trauma on the stress response system had to have been permanent. "The stress of being a POW was so severe it changed the way these folks responded to stress in the future--it sensitized them."
Their neurohormonal system was kicked off-kilter. Instead of churning out the normal amount of hormones in the face of stress, their systems were now so deregulated that at the slightest provocation, they either pumped out too much of some chemicals needed or not enough of others. "Years of this kind of hormonal assault may have weakened their cardiovascular systems and led to the strokes," Brass says.
Brass was unable to document actual changes in the neurohormonal system. But another study, of child abuse victims, reported at a meeting of the American Psychiatric Association, provides some of the earliest proof that stress can physically alter people. With magnetic resonance imaging, researchers took pictures of the brains of 38 women, 20 with a documented history of sexual abuse, 18 without. Among those women sexually abused as children, the researchers discovered, the hippocampus is actually smaller than normal. A tiny seahorse-shaped structure in the middle of the brain, the hippocampus is partially responsible for storing short-term memory. It is activated by some of the same neurohormones released during stress. "What we are seeing," says Murray Stein, Ph.D., of the University of California at San Diego, "is evidence that psychological stress can change the brain's makeup."
If stress sensitization begins with a major trauma and results in wholesale neurochemical and neuroanatomical changes, there should be other examples of its ravages. Perhaps, but they won't be easy to find, says UMass's King. "Most kids who suffer a trauma are not brought to the doctor," she says. "They get through the problem, go on with their lives, and wind up in our offices years later, suffering from depression or heart disease. And unless we were able measure amounts of hormones released before the initial exposure to stress, we wouldn't know if the levels were elevated." So researchers are looking at laboratory animals.
Even the lowly rat appears to become sensitized to stress. One study at UMass found that rats repeatedly stressed by exposure to a life-threatening cold and being deprived of maternal contact immediately after birth became hyper responsive to stress. "Rats stressed from birth had a blunted release of ACTH in response to later stress," reports King. Then she reexposed them to cold after the age of 14 days, when their hypothalamic-pituitary axis matures. "Without enough ACTH, the rats were less able to mount a fight-or-flight response. The trauma of the early stress seems to have altered their response system."
"Hormonal changes from stress sensitization are quite clear in animals," notes Delaware's Levine. His own studies of monkeys document permanent changes in cortisol output in response to stress among monkeys subjected to early psychological trauma. "What's interesting are the fine variations in the changes depending on the type and time of the trauma," Levine says.
For instance, monkeys separated from their mothers for a mere 15 minutes a day during the first few months of life develop a stress response system that is slightly muted, compared with monkeys reared normally. But if the monkeys are separated from their mothers for a full three hours a day during the first few months, their later response to stress is hyperreactive. These sensitized monkeys literally run around the cage or cower in a corner in the presence of other nonthreatening animals.
"At first this may appear contradictory, but actually it is logical," Levine explains. "Being separated from their mothers for a few minutes a day is stressful, but not traumatic. It is not life-threatening, and so the animals did not have to develop a different set of mechanisms to get through that time. The muting of their stress response can be seen as a kind of defense against this daily intrusion," as if the monkeys are telling themselves "why get all worked up over this when I know it soon will be over."
"On the other hand, being separated from their mother for three hours a day is very traumatic," observes Levine. "Anything can happen during that time, so the monkeys must develop a heightened sense of awareness to protect themselves. This need may permanently alter their response so it is hyperresponsive all the time."
Is the same true for us? "We do know that sensitization happens, but we don't know what kind of stress it takes or when the stress must take place in order to produce the changes. There are a lot of variables in humans that are very difficult to control for, like the emotional environment in the home, genetic susceptibilities, and more. Some factors may cancel out the effects of an early trauma. We don't know."
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