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Stress linked to memory impairment

June 14, 1999

NEW YORK (Reuters Health)--Prolonged stress can cause the memory to fail, report U.S. researchers.

A study in human volunteers shows that exposure to high levels of the stress hormone
cortisol can impair what scientists call "verbal declarative memory," or the ability to remember words, details, and phone numbers.

The hormone, which is produced by the adrenal glands during physical and
psychological stress, can interfere with the ability to recall verbal information because
of its effects on the brain, according to a report published in the June issue of the
Archives of General Psychiatry.

Every day for four days, 51 people were given a dose of cortisol mimicking a
mildly stressful event, a higher dose mimicking a major stress, or a placebo
(inactive drug). About 93 percent of those given the higher dose of the hormone had
more difficulty recalling information in a paragraph read to them compared with
those given low doses or a placebo, report the researchers.

Six days after the cortisol treatment was halted, all the groups in the study performed
equally well on memory tests, suggesting that high levels of the stress hormone
were responsible for the previous poor showing on these tests in the high-dose
cortisol group.

The investigators suggest that "several days of exposure to cortisol at doses and
plasma concentrations associated with physical and psychological stress in humans
can reversibly decrease specific elements of memory performance in otherwise
healthy individuals."

The high dose of cortisol used in the study was roughly equivalent to "the kind of
physical stress that occurs during a major abdominal surgery," said lead study
author Dr. John Newcomer in an interview with Reuters Health.

Newcomer also compared this high level of stress to "the psychological stress when
Kosovars saw their relatives murdered, their villages burned, and were forced to
leave the country."

It is possible that mild stress may also cause some people to produce a large amount
of cortisol, and thus have some impact on memory. Or people who are under
chronic stress may develop a tolerance to high levels of the hormone, according
to Newcomer, an assistant professor of psychiatry and psychology at the
Washington University School of Medicine in St. Louis, Missouri.

Cortisol appears to be "responsible for changing the way energy is being used by
different tissues," said Newcomer. In particular, the hippocampus, a region of the
brain that plays a key role in memory, has a particular abundance of receptors
than bind to cortisol.