Benefit finding and diurnal cortisol after prostate cancer: The mediating role of positive affect.

Abstract

Benefit finding (BF) has exhibited a salutary effect on psychological adjustment to cancer. However, few studies have examined its relationship with physiology or have examined BF in men with cancer. This study investigated whether BF is associated with hypothalamic-pituitary-adrenal axis activity (ie, diurnal salivary cortisol) in men treated for prostate cancer. Positive affect (PA) is proposed as a potential pathway linking BF to diurnal salivary cortisol. A sample of 66 men treated for localized prostate cancer within the prior 2 years completed questionnaires and collected salivary cortisol 3 times per day over 3 consecutive days. Hierarchical linear modeling was used for estimating the effects of BF and PA on cortisol responses as measured by diurnal slope and area under the curve (AUCg). Confidence intervals for indirect effects were estimated using the Monte Carlo method for mediation testing. BF was significantly associated with diurnal cortisol slope, controlling for body mass index and age (B=-.12, P=.03), such that greater BF was associated with steeper cortisol slope. Analyses revealed that PA mediated the effect of BF on cortisol slope (Monte Carlo estimation 95% CI=-0.087, -0.001); negative affect did not mediate this relationship. BF was not significantly associated with AUCg. Deriving more benefit from one's experience with prostate cancer is associated with a healthier diurnal cortisol rhythm. Through its potential to enhance PA, the relationship of BF and physiological processes underscores the health relevant value of BF in prostate cancer survivors.