Box 1. Neuroendocrine Correlates of Social Support
Some of the strongest links between psychosocial factors and cancer come from studies of social support. These studies suggest that in the context of cancer, social support may modulate key neuroendocrine mediators of tumor progression, including norepinephrine, cortisol, and oxytocin. These mediators are thought to underlie the social support-immune relationships and social support-tumor relationships discussed in the review.
High social support has been associated with lower mean salivary cortisol in metastatic breast cancer patients 74 and with steeper diurnal cortisol slope in ovarian cancer patients surviving more than 5 years. 75 Social support may also modulate signaling through the sympathetic nervous system. Higher levels of social attachment (emotional social support) were associated with lower levels of both tumor and ascites norepinephrine in ovarian cancer patients. 76 Similar associations have been observed in childhood cancer patients, where social support from friends predicted lower urinary norepinephrine, and self-worth and family support were related to lower urinary epinephrine. 77 Additionally, at the time of surgery, ovarian cancer patients reporting higher levels of the facet of social support involving nurturing of others aspect had higher levels of tumor-associated oxytocin. 78 Taken together these findings indicate more normalized neuroendocrine profiles associated with social support.
It may also be important to distinguish between negative aspects of social support (such as criticism or social constraints) and positive aspects of social support, and to consider that they may have differential effects, and that negative social support may be qualitatively different than social isolation. Illustrating this point, one study of 181 breast cancer patients found that high levels of negative social support were associated with a flatter (less healthy) diurnal cortisol slope, but in contrast to findings in other labs, found no relationships of positive social support with cortisol slope. 79
Social support has important implications with respect to clinical prognoses in cancer patients. For example, among epithelial ovarian cancer patients, those with greater social support had an approximately 13% lower risk of death, controlling for clinical covariates. 80 A meta-analysis including 87 studies of cancer patients reported that high levels of perceived social support were associated with a 25% decreased relative risk for mortality, and presence of a larger social network and being married were associated with 20% and 12% decreased relative risk for mortality, respectively. 27
It is not clear what elements of social support are most potent in driving the neuroendocrine-immune-tumor cascade. It is possible that an increased sense of safety, opportunities for emotional expression, feeling understood or supported by others, or a sense of efficacy may reduce threat physiology and be driving some of the neuroendocrine processes underlying these effects.