What causes depression in cancer patients?

• Why is it that cancer patients are more ptone to depression?
• Research has shown that tumours produce chemicals which enhances negative mood swings. Further cancer is associated with depression. According to experts,this could be due to either a result of trauma of diagnosis, or possibly a side effect of chemotherapy. The third possibility is that 2 types of tumours induced molecules, one secreted by the immune system and another by the stress axis.
• Research on rats showed that the rats with tumours had increased levels of cytokines in their blood and in the hippo-campus, a portion of the brain that regulates emotion. The increase in cytokines are linked to depression.