By Amy Norton
NEW YORK (Reuters Health) - Cancer patients suffering from depression appear to have poorer survival than those without the disorder, and the depression itself may play a part, researchers reported Monday.
In a review of more than two dozen studies of cancer patients, the researchers found that patients diagnosed with minor or major depression had a 39 percent higher death rate in the years following diagnosis.
In addition, patients who screened positive for depression symptoms but were not formally diagnosed had a 25 percent higher death rate than those without significant symptoms.
When the investigators looked at factors that could explain the findings -- such as more-extensive cancer, older age or higher rates of smoking among depressed patients -- the link between depression and survival remained.
This suggests that the mood disorder itself may play a role in cancer patients' survival, the researchers report in the journal Cancer.
The question of why cannot be answered by this study, lead researcher Jillian R. Satin, of the University of British Columbia in Vancouver, Canada, told Reuters Health in an email.
But other research suggests that depression could influence survival either by direct physiological effects --including dampened immune- system functioning and hormonal changes -- or less directly, by altering patients' lifestyle habits or ability to follow their treatment regimens.
Satin's team based its findings on 27 studies that looked at the relationship between depression and mortality among more than 9,400 cancer patients. Eleven of the studies followed patients for five years or more.
Across three studies that focused on formally diagnosed depression, patients with the disorder had a 39 percent higher death rate. Across the 24 that assessed depression symptoms, patients with symptoms had a 25 percent higher death rate.
The researchers stress that those figures represent relative differences between large groups of patients -- not the actual risk to any one person.
"It is clear that an effect is present, but it should be kept in mind that the increased risk is quite small," Satin said.
But regardless of whether and to what extent depression directly affects cancer survival, the problem should be addressed, according to the researcher.
"It is my stance that depression should be treated in cancer patients, for its own sake," Satin noted, "and not only for its potential to increase mortality."
She added that while cancer patients should not "panic" if they are feeling depressed, "I am certainly in favor of promoting dialogue between patients and their physicians about mental health during the course of illness."
SOURCE: Cancer, online September 14, 2009.
