Can you really scare someone to death?

The idea of people scared to death is nothing new. At the turn of the 20th centur­y, Sir Arthur Conan Doyle wrote "The Hound of the Baskervilles." In this mystery, Sherlock Holmes invest­igates the case of a man who had a heart attack seemingly caused by fear of a ghostly dog haunting the area. The man, Charles Baskerville, was particularly susceptible to the stress of the deadly dog because of his heart condition. Doyle was also a practicing physician, and a century after the tale's publication, researchers from the University of California at San Diego set out to see how much of his real-life work might have informed his fiction.

­To examine what they termed the "Baskerville effect,­" or dying of a heart attack brought on by intense psychological stress, the researchers examined death certificates to see if a cultural fear brought on death. In Chinese and Japanese cultures, the number four has extremely unlucky connotations, because the pronunciation of it is so similar to the word for "death." Even in the United States, some Chinese and Japanese people try to avoid travel on the fourth of each month; you might occasionally see a menu without fours or a building without a fourth floor.

Researchers hypothesized that if Chinese and Japanese people were unnerved by the date, then there could be a spike in cardiac-related deaths on that day caused by stress. They examined the death certificates of about 200,000 Chinese and Japanese people over a period of 25 years, with a control group of 47 million white people [source: Phillips, et al.].

­

­­

The researchers found that Chinese and Japanese mortality was indeed higher on the fourth of the month as compared to the white control group. For the Chinese and Japanese group, there were 13 percent more cardiac deaths than expected on the fourth of each month, and the numbers only went up in California, where large populations of those ethnic groups are located, indicating that more people are raised with a cultural fear of four [source: Phillips et al.]. The researchers examined nine alternatives that might explain why deaths would be higher on the fourth, including a superstitious person avoiding hospitalization on that day, but they found no compelling links.

­The study of the Baskerville effect is significant because it represents one of the few ethically responsible ways to conduct research on being scared to death; it isn't, after all, appealing to sign up for a study in which researchers will present you with your worst fear only to see if you're still standing afterward. But this study primarily considered people with existing cardiac conditions; what of those who walk around perfectly healthy? Could a scary encounter send them 6 feet under? Go to the next page to find out.

While we all know the importance of taking care of the ticker, there may be some fear triggers that we just can't avoid, like a terrorist attack or an earthquake. Take the day of Jan. 17, 1994. That was the day the Northridge earthquake struck Los Angeles. On a normal day in Los Angeles, about five sudden deaths occur; a sudden death is generally defined as a natural death (usually attributable to heart disease) that occurs unexpectedly in someone who hasn't previously exhibited life-threatening symptoms or conditions. On the day of the earthquake, there were 24 sudden deaths [source: Harvard]. A few were linked to physical exertion, but most were attributed to the frightful earthquake. While the average age of the people that died that day was fairly high -- 68 years -- only 42 percent of those people had previously exhibited symptoms of heart disease [source: Harvard].

How often does this happen? It's hard to say, because most accounts of sudden deaths in otherwise healthy people are anecdotal. One of the most famous reports of sudden death was published in 1942 by Harvard physiologist Walter B. Cannon. Cannon reported on a phenomenon that he called "voodoo death." The physiologist noticed that sudden deaths had a habit of occurring in places where some form of voodoo or black magic was practiced, including South America, Africa, Australia and New Zealand. He recounted the sudden deaths of healthy men who had been cursed by a medicine man, accused of eating forbidden food items and injured by spears that were said to be enchanted. Though Cannon noted that many of the men may have brought about their own deaths by refusing food and water, they essentially died because of a fear perpetuated by their society.

Cannon attributed the ultimate cause of death to an overactive sympathetic nervous system. Essentially, the sympathetic nervous system activates the fight-or-flight response we spoke of earlier. But the response is never shut down. Instead, the jolt of adrenaline acts on the heart almost like a large amount of cocaine would -- it completely shuts the organ down. At the same time, the fight-or-flight response causes the blood vessels to constrict so that valuable oxygen is cut off from the heart, further compounding the body's distress.

Walter Cannon ended his 1942 paper with a request that anyone who observed a case of voodoo death try to conduct more tests upon the subject; unlike the researchers on the last page, he lacked an ethically responsible way to study voodoo death. That gives some tales of getting scared to death the ring of urban legend.

A small group of researchers, however, continues to follow the trail blazed by Sir Arthur Conan Doyle and Walter Cannon. Boston neurologist Martin A. Samuels, known as the "death doctor" to his colleagues for his tales of eccentric sudden deaths, believes that the sudden death of former Enron CEO Kenneth Lay in July 2006 could have been the result of fear of a looming prison sentence [sources: ABC, Das]. Researchers at Johns Hopkins University studied the effects of the "broken heart syndrome," in which extreme emotions caused something that looked like a heart failure or heart attack, but that was, in fact, different, because the blood clots and clogged ­arteries­ that cause cardiac conditions were absent [source: Grady]. Instead, the heart was just weak from stressful emotions.

This work suggests that death could happen in the wake of any shocking emotion, from intense joy at finding out a long-lost son is still alive, to deep anger at the betrayal of a loved one. Hypothetically, that means we're all at risk. But since millions of us engage in scary movies, haunted houses and rush hour traffic every year, it's hard to imagine that getting scared to death is a real threat, and both Samuels and the researchers at Johns Hopkins acknowledge that the risk of sudden death from fear or any emotion is low.

Still, it's worth thinking twice about throwing that surprise birthday party for Grandma this year. While you ponder, see the links on the next page for more stories on the things that could frighten you into your grave.

­