Researchers from the National Institute on Aging found older people who are chronically depressed (depressed for at least six years) had an 88 percent higher risk of developing cancer. The higher risk was consistent for most types of cancer and not specific to cigarette smokers. The study appeared in the December 16, 1998, issue of the Journal of the National Cancer Institute.

The researchers analyzed data on 4,825 men and women, aged 71 and over, from East Boston, Mass., New Haven, Conn., and two counties in Iowa. Of this group, 146 were chronically depressed.

Researchers checked Medicare records to determine which patients had developed cancer. After adjusting for age, sex, race, disability, hospital admission, alcohol intake, and smoking, the researchers found the chronically depressed group had an 88 percent higher risk for developing cancer, compared with older persons who were not chronically depressed.

According to the study, antidepressants did not affect the cancer rate, and the link between cancer and depression was not due to any differences in drinking, smoking, or body weight. The dietary preferences of depressed people, such as foods high in fat, may partly explain the study's findings, the researchers observed.

What Depression Does
Depression has been shown to cause immune suppression, which can affect the immune system's ability to find and fight cancerous cells. Although depression has been suggested as a predisposing factor for cancer, previous studies have been inconclusive. The researchers said theirs is the first study to look at the association between cancer and chronically depressed mood. Previous studies looked at only single episodes of depression to see if a link between cancer and depression could be found. There does not appear to be a relationship.

"These findings need to be replicated elsewhere, especially since the study included only 146 chronically depressed people aged 71 years and older when enrolled," said Michael Thun, MD, vice president for epidemiology and surveillance research for the American Cancer Society. "It is interesting the association was seen even in lifelong nonsmokers. The study largely preceded modern antidepressants, and does not shed light on whether these medications may modify risk."