Depression and cancer: no clear connection.

Depression and cancer: No clear connection

Disease and depression seem to go hand in hand. If you get sick, you may feel depressed. But can feeling depressed cause disease? Past research has indicated depression can compromise the immune system, and a few studies have hinted at a link between depression and cancer.

Epidemiologists now reports that chronic feelings of depression do not affect a person's likelihood of developing cancer. They draw this conclusion from what they say is the first nationally representative study of depressive symptoms and cancer incidence among U.S. adults.

In 1971, Alan B. Zonderman and his co-workers at the National Institute on Aging's research center in Baltimore began looking for symptoms of depression among 6,913 people participating in the National Health and Nutrition Examination Survey, conducted in numerous communities across the nation. Ten years later, they retested participants and found tht most high scorers retained their depressive outlook. They then compared the cancer incidence of the high and low scorers. As a further check, they counted new cancer cases among elderly participants after 15 years. In both cases, high scorers showed no greater tendency than low scorers to develop cancer, the team reports in the Sept. 1 JOURNAL OF THE AMERICAN MEDICAL ASSOCIATION.

Zonderman cautions, however, that the study sheds no light on how depression might affect the course of an already-diagnosed cancer.

He stresses that his team did not measure clinical depression per se. Instead, they asked participants to complete the "cheerful vs. depressed" part of the General Well-Being Schedule, a standard inventory of depressed feelings experienced during the past month. To double-check the results, they also gave some participants the Center for Epidemiologic Studies Depression Scale. "The instruments we used can predict who's likely to be clinically depressed, but it's not the same as making a diagnosis of depression," Zonderman says.

The researchers obtained cancer diagnoses from death certificates and hospital records. In the group with depressive symptoms, they found, 11 percent suffered some form of cancer, compared with 10 percent of those without such symptoms.

Zonderman says the lack of a significant difference in cancer incidence "calls into serious question the hypothesis that depressive symptoms are a risk for cancer mordibity or mortality."

But Karl Goodkin of the University of Miami says he finds that broad conclusion unwarranted. Depression might influence different types of cancer in different ways, he says. "Since [Zonderman and his colleagues] don't stipulate which tumors are picked up in their sample, we don't know whether their results are supportive of depression's effect on [the incidence of] viral tumors or not," he argues. Noting that his and other research on virus-caused cancers suggests depression and stress may increase the likelihood of precancerous tissue developing into full-blown tumors, Goodkin contends that Zonderman's practice of pooling all cancer types could bury a link between depression and certain cancers. Paradoxically, he adds, animal research has suggested that stress may limit the growth of nonviral malignancies. "There may be two strong, opposite effects hidden by mixing all types of cancers," he speculates.