State associations with the cortisol awakening response in healthy females

The current study examined intra-individual relationships between the cortisol awakening response (CAR) and state sleep-related and psychosocial variables in a pooled design study. 12 healthy female participants (age range: 22-41 years.) were examined on 12 study days each, occurring at three-day intervals. Quantitative diaries capturing state sleep-related and psychosocial variables were filled out on the evening before each study day as well as 45min post-awakening on the study day. On each study day, salivary free cortisol was determined at 0, 15, 30, and 45min post-awakening. Relationships between cortisol measures and psychosocial variables were analysed using dummy-variable linear regression models. State variability in the CAR (area under increase curve; AUC(I)) was found to be inversely related to simultaneous variability in awakening time (beta=-.29, p<.005) and positively related to variability in adverse psychosocial states of stress (beta=.22, p<.01) and tension (beta=.32, p<.001) measured 45min post-awakening. In addition, levels of the CAR were also found to decrease linearly over the study period across participants (beta=-.19, p<.01) and this time trend could not be explained through a relationship between the CAR and any of the examined variables. The results are discussed within the context of previous evidence and potential implications for cross-sectional research are highlighted