The Usual Suspect

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.

 

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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.