The Surprising Ways Stress Affects Your Health

Walter Bradford Cannon did not strike people as someone interested in black magic. A world-famous physiologist, Cannon often wore three-piece suits in his laboratory at Harvard Medical School. He spent his life making very precise measurements of bodily functions and drawing cautious conclusions from those measurements. That's why his colleagues were surprised by the paper that Cannon published in the American Anthropologist in 1942. In it he described well-documented examples of healthy young adults in South America, Africa, Australia, New Zealand, various islands of the South Pacific and Haiti who had been hexed by witch doctors. Once the word of their hexing was out, the victims were often abandoned by their tribe and even by their families. Within a few days, they were dead. These "voodoo deaths" just happened, without any discernable violence having been done to the victims. Black magic, it would seem. Cannon had an alternative explanation, however: he believed the victims had been scared to death.

Cannon was the first to describe the "fight or flight" reaction: when the brain perceives a serious threat, it sends chemical and electrical signals that prepare the heart, lungs, blood vessels and immune system for the battle or chase to come. Cannon pointed out that—in a world full of sudden physical threats—this stress reaction helped preserve the lives, and hence the reproductive capacity, of human beings; it thus had been fostered and preserved by evolution. In the case of the voodoo victims, however, Cannon argued that the stress reaction was harmful rather than protective. When the reaction remained activated for several days—sustained by fear and aggravated by a loss of social support—it led to a collapse of the circulation and death.

While there is much evidence linking stress to the heart and blood vessels, the relationship is not nearly as simple as a recounting of Cannon's voodoo paper might suggest. And despite some widely held and popular ideas, the link between stress and other diseases is even less clear. Surely, experiencing stress may worsen the symptoms of almost any condition. But there is little evidence that stress is the exclusive or even the principal cause of any disease.

For decades, we believed that stress led to an overproduction of stomach acid, which caused duodenal ulcers. Stress does increase the amount of acid produced in the stomach, and there's no doubt that, once a person has a duodenal ulcer, acid makes the ulcer hurt. But we now know that the ulcer's cause is not stress but a bacterial infection, curable with antibiotics. Doctors also once believed that the inflammatory bowel diseases—Crohn's disease and ulcerative colitis—were caused by stress. Today we know they are caused by inherited tendencies toward abnormal inflammation in response to gut bacteria. Treatments based on that theory do a lot more to relieve symptoms than does stress management. There also is little evidence that stress causes asthma, although some patients have flare-ups more often at times of stress. And despite much folklore, there is no proof that stress causes cancer or worsens its prognosis. Stress-reduction programs can be very helpful in easing the suffering of a victim of cancer, but there is no strong evidence that they lengthen life.

It's the role of stress in heart disease that has received the most attention over the years, and with good reason. Like our ancestors, we all occasionally face the single, sudden and extreme stressors that the stress response evolved to protect us from. For us, the acute stressor may not be an approaching pride of lions, or the knowledge that we have just been hexed and therefore soon will be dead. Rather, it may be a car that has run a red light and is hurtling toward us. Our response to such sudden and extreme stressors can protect us, but it also can have dire consequences if we already have heart disease.

Perhaps even more important is the drip-drip-drip of chronic, low-grade stressors—the traffic jam that means we'll be late for an appointment, worrying about how to pay the bills this month, or recurring tension with a spouse or child. These chronic stressors, like sudden and acute stressors, also can affect the most common and lethal form of heart disease we face—atherosclerosis (sometimes called "hardening") of the coronary arteries.

Coronary atherosclerosis deforms artery walls. Ultimately, it can block blood flow, starving the heart muscle of the nutrition it needs. (Article continued below...)

Plaques of atherosclerosis cause symptoms two ways. If the plaques grow large enough to significantly obstruct the flow of blood, the heart won't get the blood supply it needs when it is forced to work harder—for example, by exercise or by anger. The heart is not actually damaged, but the pain can recur whenever the heart is again forced to work hard. Alternatively, a plaque can rupture, either when the heart is working hard or even when a person is at rest and at peace. Plaque rupture causes a blood clot to form that suddenly and often completely stops the flow of blood through the artery.

Chronic stressors can speed the development of atherosclerosis and enhance the dangers from it once it has developed. They can also contribute to heart disease indirectly if they lead us to overeat, under-exercise or smoke. Stress is a toxic emotional and physical response; anger, hostility, depression and anxiety are examples of such toxic responses. Anxiety, for instance, involves apprehension combined with palpitations, fatigue and shortness of breath. Some people respond to chronic stressors with remarkable equanimity. Others spend a substantial fraction of their day experiencing one or more of the toxic reactions. This is influenced in part by our genes, but is also controllable with stress-management techniques. And if these toxic reactions are not controlled, there is growing evidence that heart disease is more likely to occur and at an earlier age.

Sudden, major stressful life events can sometimes cause catastrophic results in people with underlying heart disease—including heart disease they didn't know they had because it had never before caused symptoms. The sudden outpouring of adrenaline in reaction to the event can cause the heart to work unusually hard, or can cause a plaque of atherosclerosis to rupture, which in turn can generate dangerous heart rhythms and sudden death.

In a paper published nearly 40 years ago in the Annals of Internal Medicine, internist and psychiatrist George Engel reconstructed the events in the hours before 170 people died suddenly. Particularly for women, Engel found that the most common trigger for sudden death was a major loss—of a spouse, of self-esteem. For men, sudden danger more often was a trigger. Subsequent evidence supports Engel's thesis. For example, sudden deaths increased immediately following the Northridge earthquake in southern California in 1994, and after September 11, 2001—and not just in New York City.

Interestingly, Engel found that sudden death also could follow a triumph or a happy ending to a long struggle. He reported the sudden death of a just-released prisoner upon returning home, a man who had just scored his first hole in one, an opera singer who was receiving a standing ovation. Even joy can rattle our silently diseased arteries. Mind you, we still should seek happiness. But Engel's study suggests that we seek it in frequent, small dollops rather than in rare surges of ecstasy.

Obviously, "voodoo death" is not a problem in developed nations. However, a recently described heart disease may be. A sudden, extremely stressful situation can flood the blood with adrenaline and cause a type of heart disease called stress-induced cardiomyopathy (it's called "takotsubo cardiomyopathy" in Japan, where it was first described). More than 80 percent of the victims of this disease are women. The flood of adrenaline causes millions of tiny arteries inside the heart muscle to clamp down. The apex of the heart is weakened, causing it to balloon out. Even though the large coronary arteries on the outside of the heart muscle are free of significant atherosclerosis, this condition can cause the same symptoms as the more typical heart disease—chest pain, shortness of breath, shock and even death. We don't yet know how common the condition is.

Despite the role of stress in some diseases, we physicians sometimes oversell stress as a medical problem. It's a doctor's job to make a diagnosis and figure out the causes of disease. When we can't, it's a problem—our problem. I'm afraid we sometimes protect our egos by invoking stress, which effectively says to our patients that their suffering really is their problem. I've seen many patients with difficult-to-diagnose diseases like multiple sclerosis or lupus who, before the diagnosis was finally made, spent months and even years going from doctor to doctor. Repeatedly, they were told, "It's just stress." As a result of this "diagnosis," the doctors felt a lot better—but not the patients. The facts are that stress can worsen the symptoms of any disease and stress management can offer relief. Stress, however, is rarely the sole, convenient explanation for a patient's suffering.

Komaroff is the Simcox-Clifford-Higby professor of medicine at Harvard Medical School and editor in chief of the Harvard Health Letter. For more information about stress, go to