(Ivanhoe Newswire) – People who receive a diagnosis of cancer are often
depressed about it.
But is that depression just the result of getting the bad news, or is something
else at play?
University of Chicago researchers who studied depression in rats with cancer
believe there’s a biological explanation. They find tumors produce substances
associated with depression and then send these substances to the brain, where
they cause depressive symptoms.
The researchers note rats are a good model for studies on depression and cancer
because the animals have no idea they have the disease and thus cannot be
psychologically “depressed” about it, so any change in their behavior has to
have another cause. In the study, rats with tumors did exhibit behavioral
changes. For example, they were less motivated to escape during a swimming test
and less excited about receiving sugar water, something normal rats highly
enjoy.
Blood work and brain studies then revealed these mice had higher levels of
cytokines than healthy rats. Cytokines, which are produced by the immune system,
have been associated with depression. The stress hormone corticosterone was
dampened in mice with tumors as well. Corticosterone is known to help regulate
cytokines.
“Our research shows that two types of tumor-induced molecules, one secreted by
the immune system and another by the stress axis, may be responsible” for the
depressive symptoms, study author Leah Pyter was quoted as saying.
SOURCE: Proceedings of the National Academy of Sciences, published online May
18, 2009
