Study Ties Stress to Breast Cancer

WEDNESDAY, Sept. 24, 2003 (HealthDayNews) -- Contrary to several previous studies, new research out of Sweden claims stress can increase a woman's chance of developing breast cancer.

But even the study's lead author, Dr. Östen Helgesson, cautions the findings left many things unknown, including how much stress might signal danger.

Helgesson, a researcher at Sahlgrenska Academy in Goteborg, Sweden, presented his findings Sept. 24 at the European Cancer Conference in Copenhagen, Denmark.

One of the problems with studying stress in relation to cancer is that the effects of stress don't manifest that quickly. While there have been some studies that show stress makes a difference in the functioning of the immune system, no one knows how that connects with the development of cancer, says Frank Baker, a psychologist and vice president for behavioral research at the American Cancer Society.

"There has been a belief that breast cancer is related to stress for hundreds of years, if not thousands of years," Baker says. "We have not been able to establish conclusive linkages between experiences of stress and the occurrence of breast cancer in studies that are prospective."

The current study is a prospective one, which is one of its strengths. Prospective means that researchers followed a group of healthy women going forward, as opposed to selecting a group of women with breast cancer and delving into their past experiences.

Helgesson and his colleagues followed 1,462 Swedish women, aged 38 to 60, for 24 years. In 1968 and 1991, the women had physical exams, filled out questionnaires, and were asked by a physician whether they had been under stress for a month or longer. The definition of stress in this case included tension, fear, anxiety or sleep disturbances connected with conflicts in the family or at work. The women had follow-up examinations in 1974-75, 1980-81 and 1992-93, but were not asked about stress again. Complete data was available for 1,350 of the women.

The stress experience related to this study was during the five-year period leading up to the 1968-69 examination.

Women who said they were experiencing stress during this period had about double the risk of developing breast cancer than women who reported that they were not stressed. The absolute numbers, however, were low: 24 of the stressed women developed breast cancer and 432 did not. Of the unstressed women, 23 developed breast cancer and 871 did not.

The study authors say they adjusted for confounding factors such as alcohol consumption, smoking, body mass index, education, family history of breast cancer and more.

Overall, all the women still fell in the ballpark of low risk, says Dr. Paul Tartter, a breast surgeon at St. Luke's/Roosevelt Hospital Center in New York City. "This group of women have a relatively low risk overall compared to American women," he says.

The women in the study also did not develop cancer at an earlier age than would be expected in the population at large.

"The good thing is the findings are not biased at all," says Helgesson, who is with the department of primary health care at Gothenberg University in Sweden. "Most other studies have been made on women who already have a lump in their breast and they're worried about death. They don't feel good."

Although parts of the methodology are strong (namely, the fact that it is a prospective study), there are also weaknesses. As the lead author himself points out, the questionnaire used, for instance, has not been validated as an accurate way of measuring stress. If more research were to be done, Helgesson says, "we would need a better stress scale. We didn't know much about this in 1968 so we produced this simple questionnaire. This is a weakness of this study."

"It's not a standardized measure of stress," Baker adds. "This research would need to be replicated with better measures of stress."

"It's intriguing," Tartter adds. "And it's what we all want to hear, that stress contributes to cancer, because we can control stress."

More information

Find more on psychological stress and cancer at Britain's National Cancer Institute or the U.S. National Cancer Institute.