Stress, immunity, and cancer

Chronic stressful experiences have been associated with various infectious diseases and the progression of various forms of cancer. These relations have been attributed to immune changes, variations of proinflammatory cytokines, diverse hormones, growth factors, and microbial changes, as well as lifestyle changes caused by stressors. In contrast to effects on cancer progression, the link to cancer occurrence is questionable, although it may be premature to dismiss this possibility entirely given that stressors experienced years earlier, including during early life, may set in motion processes that predict later cancer occurrence. Comorbidities frequently occur between various illnesses (e.g., depression and cancer), which may be related to stressors and may be mediated by shared biological mechanisms, particularly those that favor increased inflammatory activity. Therapies to diminish the influence of stressors and depression might influence cancer progression, but even if they do not, the quality of life among patients may be enhanced.