High levels of cortisol, the stress hormone can temporarily impair memory, according to a study published in the current issue of Archive of General Psychiatry . The study suggests certain parts of the brain involved in memory may be demoted to a temporary status "non-essential" in severe stress.
Previous studies have shown that high doses of synthetic glucocorticoids, which are used as drugs to treat diseases such as asthma and lupus, can cause brain damage and memory problems. Psychiatrist John Newcomer of Washington University in St. Louis decided to examine whether cortisol, a natural glucocorticoid that acts as a stress hormone, has the same effect at levels that can occur in the body. Cortisol helps jump-start the fight-or-flight stress the body by ordering more glucose circulating in the blood.
twice daily for 4 days, 51 healthy volunteers ingested either a high dose of cortisol (0 mg), a lower dose (40 mg) or placebo. The high dose "is not like having a bad day at the office," said Newcomer; rather, it would be caused by things like undergoing major surgery, "walking 50 miles to a refugee camp in time of war, or have a very sick child, "he said.
After one day, the volunteers performed as well when asked to listen and remember later paragraphs of text containing about 0 separate pieces of information. But after four days, 93% of individuals in the high dose group displayed a significant decrease in memory, recalling details about 20 less than the other groups. A week after the experience, however, all subjects did just as well again. The researchers hypothesized that increased levels of cortisol somehow prevent the transport of glucose into the cells of the hippocampus, a brain structure known to play a role in memory, temporarily depriving them of energy benefit other organs.
"It should be noted that the impairment did not occur after a single episode," says neuroendocrinologist Bruce McEwen of Rockefeller University in New York City. "The brain is somewhat protected from the stress because it does not effect immediately and show these effects are fully reversible" Newbie and his group would identify the specific blood cortisol level that begins to interfere with memory. They hope doctors can possibly use a blood test to eliminate stress as a cause of memory problems in their patients.
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