Does Stress Cause Breast Cancer?

Swedish Study Suggests That Chilling Out now Could Lower Breast Cancer Risk Later

From the WebMD Archives

Sept. 24, 2003 (Copenhagen, Denmark) -- As if life isn't stressful enough, Swedish researchers say that being under stress maydouble a woman's risk of developing breast cancer.

They based their findings on surveys of more than 1,400 Swedish women in the late 1960s who were part of a long-term health-care study.

The women, who were reported to be a representative sample of the Swedish population, were asked to fill out a health survey, which included a question about stress, asking whether at any time in the last five years they had experienced a feeling of stress for a month or more.

Examples of stressful situations the women might have encountered were tension, fear, anxiety, or sleep disturbances related to family or work problems. Because the question about stress was only one of many different questions asked at the time, the researchers felt that their answers would probably have accurately reflected the way they felt at the time, says Oesten Helgesson, MD, a physician in the department of primary health care at Gothenburg University.

Although other studies have looked at the question of whether stress can contribute to breast cancer, those studies were based on reports from individual patients who were already diagnosed with cancer, and that could skew the results, says Helgesson, in an interview with WebMD at a European cancer conference here.

"The women sit in a room with a lump in their breast and they get a form to fill about stress, and that could introduce bias. That's why we looked at this question," he tells WebMD.

The women were part of a study that included an initial examination and detailed health questionnaire, and regular follow-up exams over the next 24 years. Helgesson and the other researchers took the information the women provided about stress at the outset of the study, and used it to determine if there was any relation between increased breast cancer risk and earlier stress.

Stress Ranks High Among Risk Factors

They found that women who reported being under stress had twice the risk of developing breast cancer as women who managed to stay cool, calm, and collected. This twofold risk held up even when they took into account other factors that might explain the increased risk for breast cancer, such as family history of cancer, alcohol use, body weight, smoking, and factors related to reproduction, such as the age when women first had their periods, the age they were when they had their first baby, and the age they were they began menopause.

Helgesson is quick to caution that the study is small and that much more research needs to be done before anyone can state with authority that stress can increase the risk of breast cancer the way that, say, smoking contributes to lung cancer and heart disease.

Two leading cancer researchers who were asked by WebMD to comment on the study agreed.

"It's always a problem with how you define stress and whether you have a large enough study population. We're not seeing all the data we'd like to see: a larger study with clearer definitions of what is stress. But it's definitely a study worth pursuing, maybe finally putting a nail in the coffin is there a link to stress, yes or no," says Harry Storm, MD, director of Cancer Prevention and Documentation at the Danish Cancer Society, based in Copenhagen.

"This is something that's under intensive study now, and there are some indications that stress may play a role in some cancers like breast cancer," said Harry Vainio, MD, with the International Agency for Research in Cancer in Lyons, France. "But we need to see larger studies where the data can be broken down to give us a clearer idea of what's going on."

Storm adds that other studies have examined the exact same question and gotten strikingly different answers. He mentioned one study of women who had suffered the death of one of their children (an extremely stressful situation) where the researchers found that there was absolutely no relationship between stress and a later risk of breast cancer.

Show Sources

SOURCES: The European Cancer Conference, Copenhagen, Denmark, Sept. 21-25, 2003. Harry Vainio, MD, International Agency for Research in Cancer, Lyons, France. Harry Storm, MD, director, Cancer Prevention and Documentation, Danish Cancer Society, Copenhagen, Denmark. Oesten Helgesson, MD, physician, department of primary healthcare, Gothenburg University, Sweden.
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