Cortisol & Psychological Functioning

Chair: Jamie M. Zeitzer Committee Member: Robert Wickham

Background: Cortisol is a steroid hormone secreted by the zona fasciculata of the adrenal glands and is critical to cardiovascular, metabolic, immunologic, and homeostatic functions. Measures of salivary cortisol, including diurnal cortisol slope, area under the curve and the cortisol awakening response are associated with a number of mental and physical health outcomes.

Methods: Two seldom used, though promising, measures of salivary cortisol are evening salivary cortisol concentrations and salivary cortisol intraindividual variability (cIIV). Thus, the aims of this dissertation were to examine whether evening cortisol levels alone are a strong indicator of stress in women with metastatic breast cancer (Study 1) and to examine how cIIV maps onto a broad measure of psychological functioning, the Big Five, as well as to physical symptoms (Study 2).

Results: Study 1 results demonstrated that the evening cortisol sample alone is 86% accurate in identifying flattened diurnal cortisol rhythms in women with metastatic breast cancer. However, evening salivary cortisol rhythms were not associated with dexamethasone suppression, while diurnal cortisol slope was. Study 2 results demonstrated small effects for associations between cIIV and neuroticism, number of physical symptoms and physical symptom severity. However, both measures of physical symptoms were no longer significant after adjusting the alpha level. Post hoc analyses revealed perceived control as a common mediator in these associations.

Conclusions: Together, these results provide further evidence for the utility of evening salivary cortisol levels and salivary cortisol intraindividual variability as sensitive indicators of HPA axis function.