Common wisdom long has maintained that stress can be a contributing factor to ill health and delayed recovery from disease. Two recent studies are backing up that lore with scientific proof.
Dr. Phillip Marucha and his colleagues at Ohio State University measured stress in mice. One group of the critters was confined in tubes for 15 hours a day so that they couldn't move around, while the other group was allowed to roam in their cages. Both were deprived of food and water during that 15-hour period.
After three days of restraint, both groups were inflicted with skin wounds, and a portion of each group also was exposed to the common bacteria Streptococcus. The stressed group continued to be confined to tubes for portions of the next five days.
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The researchers found that 85 percent of the stressed mice became infected with strep while only 27 percent of the non-stressed mice showed signs of infection. The levels of bacteria in the stressed mice were about 100,000 times that found in the wounds of the non-stressed mice. "That's an astounding amount," said Marucha.
"The bottom line was that stress shuts down either the recruitment or the function of immune cells needed to fight infection," he said. Other researchers have found lower concentrations of disease-fighting cytokines in the skin of women who are under stress, suggesting that stress affects humans about the same way.
At the UCLA AIDS Institute, researcher Dr. Steve Cole studied the autonomic nervous system ( ANS ) activity of 13 HIV-positive men, age 25 to 54. ANS is a series of measurements of things like blood pressure, heartrate, etc. "People with higher ANS activity tend to be more high-strung and easily stressed out," explained Dr. Jerome Zack, who assisted with the research.
The patients started a combination therapy for their HIV while the doctors monitored their ANS, CD4 T-cell count, and viral load. They found that the level of stress was a powerful predictor of response to therapy.
Viral load dropped 40-fold in those with low levels of stress and less than 10-fold in those with high levels of stress. Five of the seven low stress men quickly reached undetectable while only one of the six men with high ANS did so.
"Those at the top of the high ANS activity group showed no immune recovery at all," said Zack. Some of them even continued to lose CD4 cells, despite starting therapy, while those "with low ANS activity rebounded from 396 to 550 CD4 cells."
The researchers went to the lab for an explanation. They exposed T-cells to the hormone norepinephrine that nerves release when under stress. They found a five-fold increase in the number of CCR5 and CXCR4 receptors on the T-cell surfaces.
The hormone was bringing more of these molecule receptors from deep within the cell to be exposed on the outside of the cell membrane. These receptors are the ones HIV uses to invade cells...stress made each cell much more vulnerable to infection.
"It's a double whammy," said Zack, "Norepinephrine enables HIV to enter the immune cells more easily and to reproduce more readily. So more virus gets in and more virus comes out, resulting in a ten-fold increase in the amount of virus produced."