Out of Balance: A New Look at Chronic Stress, Depression, and Immunity

Chronic stress is typically associated with suppression of the immune system, including impaired responses to infectious disease and delayed wound healing. Recent work suggests that stress and depression can enhance production of proinflammatory cytokines, substances that regulate the body's immune response to infection and injury. We provide a broad framework relating stress and depression to a range of diseases whose onset and course may be influenced by proinflammatory cytokines, particularly the cytokine interleukin-6 (IL-6). IL-6 has been linked to a spectrum of chronic diseases associated with aging. Production of proinflammatory cytokines that influence these and other conditions can be directly stimulated by chronic stress and depression. We suggest that a key pathway through which chronic stress and depression influence health outcomes involves proinflammatory cytokines. We discuss the evidence for relationships between psychosocial factors and proinflammatory cytokines, and important health implications of these findings.