Receiving the news of a cancer diagnosis is something that no one wants to here. Moreover, it has been well documented that a cancer diagnosis can sometimes lead to depression in patients. However, according to research published in the Proceedings of the National Academy of Sciences (PNAS) journal, researchers found that the tumors themselves can also affect the chemical make-up of the brain and potentially cause depression.
Tests have shown that animals with tumors had increased levels of chemicals called cytokines in their blood and in the brain. Cytokines are chemicals that are produced by immune systems and have been linked to depression. Researchers tested rats bred to have cancer and found that they were less likely to try to escape when forced to swim through water or to eat a treat of sugar water, typical signs of depression.
Rats are commonly used to test drugs that are being studied for potential human benefits, such as treating depression, said Brian Prendergast, from the University of Chicago, who led the study. In this case, examining behavioral responses to tumors in non-human animals is particularly useful because the rats have no awareness of the disease, and thus their behavioral changes were likely the result of purely biological factors.