The Depressing Thing About Cancer

Sara Hartley
Medical Writer, MDLinx Oncology

It has long been known that individuals with cancer are at much greater risk for depression, anxiety and other mood disorders compared to healthy individuals. Studies suggest that at least 25% of patients hospitalized for cancer meet criteria for major depression, and the prevalence is even higher for those with breast, lung, or pancreatic cancers. 

Co-morbid depression is strongly associated with treatment noncompliance and decreased survivorship in cancer patients—underscoring the profound clinical significance of this condition. A number of factors are speculated to play a role in cancer-related depression, including subjective disease awareness, side effects of chemotherapy, and direct biological effects of the tumor. However, the relative contributions of each of these factors in the pathogenesis of cancer-associated depression remain largely unknown. 

Now researchers at the University of Chicago report some of the first evidence to show that peripheral tumors secrete substances into the bloodstream that act on the mood controlling centers in the brain. The researchers used a drug to induce mammary tumors in rats and then studied their behavior before and after tumor development. Compared to controls and drug-treated rats prior to tumor development, rats with mammary tumors exhibited high levels of depressive behavior, such as decreased motivation to escape a swimming test and reduced interest in drinking sugar water. Moreover, the tumor-bearing rats had significantly higher levels of certain cytokines (e.g., IL-1beta, IL-6) in the blood and brain, and impaired gene expression in the hippocampus—a major emotion-regulating center in the brain.

Together, these findings strongly suggest that tumor cells can secrete humoral factors that influence mood, and argue that depression should be added to the list of paraneoplastic syndromes.

Source

Pyter LM, Pineros V, Galang JA, et al. Peripheral tumors induce depressive-like behaviors and cytokine production and alter the hypothalamic-pituitary-adrenal axis regulation. Proc Natl Acad Sci. USA. 2009;106(22):9069-74.