Associations between psychosocial state variables and the cortisol awakening response in a single case study

The current study investigated intra-individual associations between psychosocial state variables and the cortisol awakening response (CAR) in a detailed case study of a 27-year-old healthy male (TS) carried out over 50 measurement days, occurring at 3-day intervals. Quantitative diaries capturing psychosocial states were filled out on the evening before each study day as well as 45 min post-awakening on the study day. On each study day, salivary free cortisol was determined at 0, 15, 30, and 45 min post-awakening. Relationships between cortisol measures and psychosocial variables were analysed using correlation analyses and relative predictive input of independent variables was further determined using linear regression analysis. Significant relationships were found between psychosocial state variables and the dynamic of the CAR (area under increase curve; AUCI). The final regression model for the AUCI (explaining ∼22% of its variability), included an inverse relationship with the level of prior-day happiness and a positive relationship with study-day anticipations of the level of obligations/no leisure. The results are discussed within the context of previous evidence and potential implications for cross-sectional research are highlighted.