Proinflammatory cytokines and sickness behavior: implications for depression and cancer-related symptoms.

PURPOSE/OBJECTIVES To review the relationship between proinflammatory cytokine release and resultant sickness behavior; to explore the implications of sickness behavior related to depression and cancer-related symptoms. DATA SOURCES Published articles and book chapters. DATA SYNTHESIS Proinflammatory cytokines (interleukin-1, interleukin-6, and tumor necrosis factor-alpha) are released as part of the immune response resulting in a syndrome called sickness behavior that is an adaptive and motivational reaction to disease. Sickness behavior includes lethargy, depression, anorexia, energy conservation, fever, anhedonia, cognitive impairment, hyperalgesia, and decreased social interaction. Sickness behavior is seen in patients with depression or cancer and has been described as a symptom cluster. Sickness behavior in patients with cancer may be the result of both the disease and the treatment. The related symptoms may have a profound effect on patients' quality of life. Treatment strategies that inhibit the release or activity of proinflammatory cytokines and relieve patients from symptoms of sickness behavior are being evaluated. CONCLUSIONS Further research is needed to pinpoint the exact effects of specific cytokines, identify targets for therapy, and develop viable treatment strategies for preventing or minimizing the detrimental effects of cytokine-induced inflammatory responses. IMPLICATIONS FOR NURSING Sickness behavior resulting from cytokine release may provide a framework to explain many cancer-related symptoms, including depression, cognitive impairment, cachexia, fatigue, and a component of pain perception. Oncology nurses would benefit from awareness and understanding of the relationship between proinflammatory cytokine release and tissue involvement by tumors as well as some cancer-related therapies. Knowledge about the effects of cytokine release on patient behavior and the symptom experience would enhance nurses' ability to assess patients for anticipated side effects and provide appropriate education to patients and their families.