Cancer Causes Depression Physically—Not Just Psychologically

Tumors may physically trigger depression by producing chemicals that induce negative mood swings, according to a new study. The research, conducted in rats, allowed for the isolation of "just the physiological effects of the tumors from the psychological effects.... The tumors themselves are sufficient to induce depression" [The Scientist], says lead researcher Leah Pyter. The new study, published in the Proceedings of the National Academy of Sciences, showed first that rats who had cancer exhibited several behavioral symptoms associated with depression. The researchers gave a forced swimming test to 100 rats, some healthy and some with cancer, and found that the sick rats did not try as hard to escape—a behavior similar to that seen in humans with depression. The sick rats were also less interested in sugar water, which is the the clear preference for healthy rats. Upon further testing, the researchers found that substances associated with depression are ...