A new research conducted by the scientists at the University of Chicago revealed that why cancer victims are more apt to become depressive.

The research conducted on rats discovered that tumours generate chemicals that in turn produce changes mood to negative.

It has already been revealed that cancer and depression are linked to each other.

Medical specialists believe that depression was likely to be either an outcome of the tension of diagnosis, or maybe fallout of chemotherapy treatment.

However, the new study has detected a third risk.

Leah Pyter, a postdoctoral fellow and lead author of a paper, stated, “Our research shows that two types of tumour-induced molecules, one secreted by the immune system and another by the stress axis, may be responsible.”

“Both of these substances have been implicated in depression, but neither has been examined over time frames and magnitudes that are characteristic of chronic diseases such as cancer,” Pyter added.

To come to the solution, the study scientists carried out a series of examination on about 100 rats, some of them were suffering from cancer.

The scientists wanted to determine the behavioral responses of rats in examinations of emotional state.

The researchers used tests commonly used in examining anti-depressants on rats and discovered that the rats having cancer tumours became less motivated to escape when submitted to a swimming test, a condition that is similar to depression in humans.

The rats having cancer also were less eager to drink sugar water, a substance that frequently draws the appetites of strong rats.

The study outcomes also showed that the diseased rats had increased levels of cytokines in their blood and in the hippocampus when compared with healthy rats.

The team also discovered that stress hormone production also was altered in rats with tumours.

The results of the study appeared in the current issue of the Proceedings of the National Academy of Sciences.