Scientists Map Ravages Of Stress On Human Health

Thanks to recent advances in biology, scientists are beginning to dope out why the myriad stresses of daily life make you feel so bad.

They are now able to see how stress, an emotional phenomenon, actually changes the physical structure and chemistry of your brain, sometimes leading to lifelong disability. And they are more optimistic than ever that they can find ways to limit or repair the damage it wreaks.

Surveys show more than half of all Americans feel they are under a great deal of stress at least once a week, according to Bruce McEwen, president of the Society for Neuroscience, an organization of brain researchers who, ironically, are meeting in the city that calls itself “The Big Easy.”

“We all differ in how we handle it, but stress is a regular experience for all of us,” said McEwen, a neuroscientist at Rockefeller University in New York.

Watching your stocks on a roller-coaster market surely can cause stress. And scientists say it can be triggered by anything from a bad day at the office or a nasty letter from the IRS to something as deeply traumatic as combat in war, sexual abuse or a baby’s lack of motherly love.

A certain amount of stress is normal and helpful, researchers said, but chronic stress leads to serious ailments.

The consequences range from trivial - like the abnormal eating pattern McEwen called the “midnight munchies” - to such crippling disabilities as ulcers, colitis, anxiety, irrational fear and major depression.

Sometimes the stress-response system becomes hypervigilant, said Michael Meaney of the Douglas Hospital Research Centre in Montreal, creating neurotic or paranoid people who “look for threats everywhere, even when they’re not real.”

With new tools like magnetic resonance imaging, researchers can now observe the physical effects of stress in the brains of humans and animals. Harmful hormones are secreted, essential cells die and pathways between brain regions essential to memory are broken.

“Only recently have we been able to go into the brain and measure what is actually happening in early life,” said Ron de Kloet, a Dutch brain researcher.

With their new understanding of stress, said Wylie Vale of Salk Institute for Biological Studies in La Jolla, Calif., pharmaceutical companies are racing to develop drugs that can counter stress hormones. The puzzle no longer seems insoluble.

Studies in rats, for example, show there is a master stress hormone known as CRH (“corticotropin releasing hormone” in the jargon of neuroscience) that governs the body’s response to stress.

Taking a 10-day-old rat away from its mother for 24 hours leads to excess production of CRH, causing fear, immobilization and memory loss. The harmful effect can be countered by stroking the baby rat for 45 seconds, three times a day, with a moist paint brush, mimicking the licking action of a mother rat, Meaney said.

Other animal studies found brain cells in infant rats break up and die when they are separated from their mother.

“These cells are committing suicide,” said Mark Smith, a psychologist at the Du Pont Merck Research Labs in Wilmington, Del. “Let this be a warning to us. The effects of maternal deprivation may be much more profound than we imagined.”

Mary Carlson, a psychologist at Harvard Medical School, reported a similar phenomenon among babies in Romanian orphanages, who lacked the tender care necessary for normal physical and mental growth.

By analyzing substances in saliva, Carlson found that some other Romanian children had higher levels of a human stress hormone, cortisol, on weekdays when they were in a badly run day-care center, than on weekends when they were with their parents.

“When a baby’s environment includes reliable parental care, it develops trust. It thinks the world is not such a bad place,” Meaney explained.

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