(NK) cells9—could help cancer to progress (Antoni and Lutgendorf, 2007; Thaker et al., 2007).

Multiple studies have shown that positive social support, in particular the provision of emotional support, is related to better immune system functioning and resistance to disease (Uchino et al., 1996; IOM, 2001; Uchino, 2006). In women with ovarian cancer, higher levels of social support predicted higher levels of NK cell activity, while patients with greater distress had more impaired NK cells (Lutgendorf et al., 2005).10 Findings from two randomized controlled trials of psychosocial interventions in breast cancer patients also found improvements in immune system functioning using a variety of measures of immune system competency (Andersen et al., 2004; McGregor et al., 2004).

Studies with animals also have found increased stress to be associated with higher levels of stress hormones (catecholamines) and increased tumor mass and metastases (Thaker et al., 2007). For example, mice with mammary tumors randomly assigned to more stressful housing conditions showed greater tumor growth as well as shorter survival following chemotherapy (Kerr et al., 1997; Strange et al., 2000). Higher levels of certain pro-inflammatory cytokines (interleukin) also have been found in people living in high-stress situations, for example, female caregivers of relatives with Alzheimer’s disease compared with community controls (Lutgendorf et al., 1999).

Although more research is needed to understand the extent to which, and how, these stress-induced physiological changes can influence cancer, it is clear that stress can induce pathology in several aspects of body function that affect health. Research findings also indicate that stress, mood, coping, social support, and psychosocial interventions affect neuro-endocrine and immune system activity and can influence the underlying cellular and molecular processes that facilitate the progression of cancer. Findings also suggest the plausibility of improving the health status of cancer patients by attending to their psychosocial distress (McEwen, 1998; Antoni and Lutgendorf, 2007; Thaker et al., 2007). For all these reasons, psychosocial stressors should not be ignored in the delivery of high-quality health care for people living with cancer.

9

A type of white blood cell that attacks harmful body invaders, such as tumors or virus-infected cells.

10

In this study, social support and distress appeared to operate independently.



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