Depression can affect the likelihood of surviving cancer, but there is no clear association yet with how quickly the cancer progresses, according to a report published on Monday.

Death rates are nearly 40 percent higher for cancer patients diagnosed with major or minor depression, according to University of British Columbia researchers who surveyed more than two dozen international clinical studies.

We found an increased risk of death in patients who report more depressive symptoms than others, and also in patients who have been diagnosed with a depressive disorder compared to patients who have not, Jillian Satin, the report's lead researcher said.

The report was published in the online edition of the American Cancer Society's journal Cancer.

Eighty-five percent of cancer patients believe their mental state affects how quickly the disease progresses, but the Canadian researchers said that belief is not actually supported by the few studies that looked at it.

The researchers admitted they were surprised by the lack of clear link between depression and cancer progression, and cautioned that may be because so few clinical studies have been done on the subject.