Researchers know that human papilloma virus, or HPV, is responsible for the vast majority of cervical cancers. But usually, when a woman is infected with HPV, the infection resolves by itself, without any medical treatment. And many more people are exposed to HPV than get cancer. Rose Hoban reports on efforts to understand what causes some women to get cancer, and others not.

Scientists have wondered what increases a woman's risk for cervical cancer once she has been exposed to HPV. And they also wonder why some people get cancer and others don't.

Studies have suggested that psychological stress is associated with decreased immune protection. Researcher Carolyn Fang from the Fox Chase Cancer Center in Philadelphia says she wanted to see if this was true with women exposed to HPV.

Fang and her colleagues recruited women who had changes on their Pap smear, the test used to detect early cell changes indicative of cervical cancer. They had the women fill out questionnaires that asked more than simply medical history.

"We asked ? about how they were feeling at that time, how they had been feeling in the past month, what kinds of events have occurred in their lives over the past six months," Fang explains.

The women were asked about two kinds of stress: one was a checklist of stressful events that may have taken place recently in the women's lives, the other was a subjective measure of how stressed they felt. Then researchers took blood samples from each subject. The blood was used in their analysis of immune response to HPV.

Fang and her colleagues exposed the women's blood samples to HPV proteins to see if the virus promoted an immune response. This indicated whether the body's defenses were working. Then they compared the blood's immune responses with what the women reported about their stress.

"Women who felt more overwhelmed, who had higher levels of perceived stress were also more likely to show an impaired immune response to HPV," Fang reports.

She says some women reported experiencing five or six recent stressful life events, but that was not associated with impaired immune responses. Fang says it didn't matter how many stressful things had happened recently; the immune response correlated most strongly to how women felt about those events.

"We all know people who managed to juggle many different responsibilities, and crises, very well," she points out. "And then in contrast, there might be that one person who is faced with one minor hassle and really comes apart. This is been found in other studies as well that it's often more how people perceive an event, how people respond or react to an event, that is more meaningful for their health, or more relevant to their health than the actual event."

Fang says these results are still quite preliminary. She says further research may show what kind of effect stress has on whether women exposed to HPV actually develop cancer.

Her research is published in Annals of Behavioral Medicine.