NEW YORK (Reuters Health) - A diagnosis of breast cancer will inevitably sink a woman's mood, but those who are able to beat that initial depression appear to survive longer, a new study suggests.

Researchers found that women whose mood lightened in the first year after being told they had advanced breast cancer outlived those whose symptoms worsened by more than two years.

But they caution that the potential mind-body connection is still uncertain, and that it's far from clear that depression is at the root of the shorter survival.

Depression can burden the body in a number of ways that are linked with cancer progression -- from decreasing immune function to increasing inflammation, according to lead researcher Janine Giese-Davis, of the University of Calgary in Alberta, Canada.

"When these physiological changes become chronic, we believe that they may deplete the resources of the body, making it more difficult for patients to recover," she said in an e-mail to Reuters Health.

Earlier research has shown more than half of cancer patients suffer some kind of depression, with around 38 percent developing major depression; the rates vary depending on cancer site and stage.

In the new study, Giese-Davis and her colleagues identified more than 100 women in the San Francisco Bay Area who had recently received a diagnosis of breast cancer that had begun spreading to other parts of the body, so-called metastatic cancer.

They randomly selected about half of the patients to undergo supportive group therapy once a week. All the women received education materials and reported their depression symptoms at four, eight and 12 months.

The researchers found that half of those whose depression symptoms decreased over the first year lived at least another four and a half years, compared to just over two years for half of those with worsening symptoms.

Improvements in depression also raised the chances of survival beyond 14 years by as much as 68 percent, report the researchers in the Journal of Clinical Oncology.

They didn't find a relationship between depression severity at the outset of the study and later survival, however, and neither group therapy nor antidepressant use appeared to affect how long women lived.

"Our results did not specify one particular treatment," explained Giese-Davis, noting that both therapy and medications can be effective. "The only thing that mattered was the decrease over time in depression symptoms."

While it is too early to be sure whether depression can truly shorten survival, she said, the finding does point to the importance of doctors, patients and their families being aware that chronic depression following an illness might take a toll.

"We do not advocate simply 'thinking positive,'" noted Giese-Davis. "It is normal for patients to feel sad, angry and fearful."

Rather, she said talking openly about those feelings could be helpful, and that overcoming depression will "improve your quality of life, your social relationships, healthy behaviors, and your ability to follow through on your doctor's recommendations."

SOURCE: http://link.reuters.com/det32r Journal of Clinical Oncology, online December 13, 2010.