Biological roots of `shell shock'


Research: Scientists uncover clues to post-traumatic stress disorder, which can be expected to afflict some survivors of recent terrorist attacks as well as soldiers.

January 11, 2002|By Michael Stroh | Michael Stroh,SUN STAFF

Jacob Mendes Da Costa, a U.S. Army surgeon during the Civil War, was among the first to study them: battle-weary warriors who sweat profusely, startle easily and exhibit irregular heartbeats.

Baffled, he and others dubbed the affliction "soldier's heart." It would be the first of many labels that doctors would give to stress-related illnesses in subsequent years: shell shock, battle fatigue, war neurosis - even battered wife syndrome, as symptoms began showing up off the battlefield.

Now, nearly 150 years after doctors first began puzzling over stress-related sickness, scientists are finally uncovering clues to its biological roots. It's a quest that has intensified in the wake of last year's terrorist attacks.

If studies of the Oklahoma City bombings hold true, as many as one-third of those directly touched by Sept. 11 could develop post-traumatic stress disorder, or PTSD, as the malady first studied by Da Costa is now known.

"There may be hundreds of thousands of cases of PTSD in New York alone," writes stress researcher Robert Ursano in this week's New England Journal of Medicine, which reviews the latest research on the disorder.

Studies with cutting-edge imaging tools and stressed-out rats are offering tantalizing clues that the brains of people with PTSD might have distinct chemical and physical quirks. A better understanding of these, researchers say, could lead to new treatments.

The research has helped silence critics who once argued that the disorder, officially recognized by psychiatry in 1980, is all in a person's imagination.

"People are not making this up," says Rachel Yehuda, director of the post-traumatic stress center at Mount Sinai School of Medicine in New York.

"Biologically, PTSD looks different from other diagnoses."

The central question driving PTSD research, she says, is why some people emerge from war, rape, earthquakes or terrorist attacks with their psyches intact while others come out permanently scarred.

The answer remains fuzzy, but the symptoms of post-traumatic stress disorder are clear. Its hallmarks include jumpiness and the tendency for traumatic memories to lodge stubbornly in the brain.

Any passing reminders of the event - a sight, a smell, a touch - can trigger intense, often debilitating flashbacks. And people with the disorder tend to go out of their way to avoid them.

For example, in his forthcoming book, Does Stress Damage the Brain?, psychiatrist J. Douglas Bremner relates the story of one PTSD patient who had been violently assaulted. The woman's attacker was drinking Coke and yanked her hair during the attack.

For a long time afterward, the woman experienced agonizing flashbacks anytime she caught a whiff of cola or felt her hair being playfully tugged by her kids.

"A critical question is why don't PTSD patients extinguish fear normally?" says Bremner, who studies the disorder at Emory University.

Of course, the ability to recall a stressful event is useful, so much so that it has been hard-wired into our brains by evolution. "Stress response," Bremner notes, "plays a critical role in survival."

If primitive man hadn't been able to recall that sprinting is usually the appropriate response to a tiger leaping at him from a bush, the human species might not have lasted very long. By studying house cats, Harvard physiologist Walter Cannon was the first scientist to piece together the biology of this "fight or flight" response, which he detailed in 1915.

This response, scientists have since discovered, triggers a complex chain reaction inside the body. Spurred by chemicals such as adrenaline and cortisol, the heart races, the pupils dilate and the liver cranks up glucose production, which primes the muscles and brain for quick action. Digestion and anything else that doesn't aid in fighting or fleeing are temporarily shut down.

In PTSD, however, researchers believe there must be a short somewhere in the fear and memory circuit, since people with the disorder can have the same stressful reaction to their loyal dog Spot leaping from a bush as they would to a man-eating beast.

Studies in the past few years are helping scientists narrow down where the problem might be. Several researchers have found that levels of the stress hormone cortisol are lower than normal in people with PTSD.

Typically, cortisol levels jump when people are stressed. One theory, says Ferris Tuma of the National Institutes of Mental Health, is that the trickle of cortisol upsets the brain's complex biochemical balance, causing traumatic memories to form more readily.

Other scientists have zeroed in on two structures central to the processing of fear and memory: the hippocampus and the amygdala.

Using magnetic resonance imaging to peer inside people's heads, scientists have found evidence that people with PTSD might have a smaller hippocampus, a structure important in memory formation.

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