Is stress making you ill? May 25, 2000 (Los Angeles) -- Many people find that they get sick more easily when they are under a lot of stress. Now researchers have found a possible reason why: The hormones our bodies release in response to stress stimulate the growth of some common bacteria. They presented their findings at a microbiology meeting here this week.

The response of the immune system to stress has been studied extensively, say authors Tesfaye Belay, PhD, and Gerald Sonnenfeld, MD. But the direct effects of these stress hormones on the growth of bacteria are not well known, they say. They decided to study the effect of human stress hormones on some of these germs.

When the researchers mixed three strains of bacteria that cause disease in a "cocktail" containing stress hormones, they found that two forms of the stress hormone adrenaline significantly enhanced the growth of two of the three types of bacteria.

"There are also reports that these hormones suppress certain aspects of the immune system," says Belay. This study, he tells WebMD, suggests that hormones produced in times of stress may increase the risk of getting an infection by stimulating the growth of bacteria in the body, as well as by suppressing the immune system. But he hastens to add that these findings are very preliminary and must be confirmed.

Still, he agrees that this might help explain why people often seem to get sick during times of stress. "These hormones somehow affect the immune system and might help promote infection." Now, he says, the challenge is to determine just how adrenaline acts on the bacteria to make them proliferate. Belay is a postdoctoral research associate in the department of microbiology and immunology at Morehouse School of Medicine in Atlanta.

Belay warns that it is too early for doctors to know just how to use this information to help their patients. Still, he says, "It is possible that effects of human stress hormones may contribute, in some cases, to the establishment and progression of some infections." Future studies will shed more light on the actions of these hormones and could help scientists learn how to temper their effects.

Vital Information:

• It is known in the medical community that stress hormones can suppress certain aspects of the immune system, increasing the likelihood of getting sick.
• Preliminary research shows that another reason stress may cause illness is because these same hormones encourage the growth of certain types of bacteria.
• Scientists do not yet know how the stress hormones work to promote infection.