MONDAY, Aug. 8, 2005 (HealthDay News) -- Despite research that depression and fatigue increase the risk of heart attack, a new study suggests they don't heighten the risk of cancer.
In fact, fatigue appears to reduce the risk of some cancers, according to the Danish researchers.
But, the most exhausted people do engage in behaviors associated with a higher cancer risk, according to the report in the Aug. 8 online edition of Cancer.
A team led by Corinna Bergelt, of the Danish Cancer Society's Institute of Cancer Epidemiology in Copenhagen, studied individuals to look for a link between a state they called "vital exhaustion" -- characterized by excessive fatigue, lack of energy, increased irritability and a feeling of demoralization -- and cancer.
They also looked at depressive mood, which has been linked by some to an increased cancer risk. Bergelt's group noted, however, that the scientific evidence is inconsistent regarding a link between depression and cancer. In fact, two recent studies found no link.
In their study, Bergelt and her team collected data on 8,527 Danes aged 21 to 94. These people completed a vital exhaustion questionnaire that also evaluated depression. During almost nine years of follow-up, the investigators looked at all cancers combined: smoking-related cancers, alcohol-related cancers, virus- and immune-related cancers, and hormone-related cancers. During that follow-up, 976 people developed cancer.
Although, Bergelt's team did find that people who had high vital exhaustion scores engaged in risky behaviors such as smoking and lack of exercise, they didn't find an association between the severity of vital exhaustion and an increased cancer risk.
To the contrary, they found that the people with the highest vital exhaustion scores had a slightly decreased risk for all cancers, virus and immune-related cancers, and smoking-related cancers. However, there wasn't a significant association between vital exhaustion and hormone- and alcohol-related cancers, they noted.
"The results of the current study show that a state of high vital exhaustion is associated with an unhealthy lifestyle," the researchers wrote.
"Nevertheless, vital exhaustion itself is not associated with an increased incidence of cancer. The results of this large, prospective, population-based study, therefore, do not support the hypothesis that subclinical depressive feelings, as measured by the vital exhaustion questionnaire, increase the risk for developing cancer," they concluded.
Cancer experts find these results surprising and think they might be limited to the specific homogeneous Danish group studied.
"It's a bit surprising that we didn't see any relationship between vital exhaustion and cancer," said Kevin Stein, the director of quality of life research at the American Cancer Society.
Stein believes the findings may not apply to other groups of people. "We cannot generalize these results beyond the two regions in Copenhagen they used," he said. "You really can't say this applies to all people all over the world."
Another expert, Dr. Julia Smith, associate director of the New York University Cancer Institute's Screening and Prevention Program, agrees the Danish findings can't be applied to other groups of people.
What's more, she believes the follow-up period wasn't long enough to include the development of all cancers. "I am not sure you can conclude, definitively, the incidence of cancer related to depression in 8.6 years," she said.
Smith also noted the researchers didn't take into account other diseases and whether any of the people in the study were taking antidepressants, which may affect cancer risk.
"You're dealing with a very specific population," she said. "I think it's interesting, but I don't think you can conclude it's definitive."
The American Cancer Society can tell you about cancer risks.