Investigating individual stress reactivity: High hair cortisol predicts lower acute stress responses.

Identifying individual differences in stress reactivity is of particular interest in the context of stress-related disorders and resilience. Previous studies already identified several factors mediating the individual stress response of the hypothalamus-pituitary-adrenal axis (HPA). However, the impact of long-term HPA axis activity on acute stress reactivity remains inconclusive. To investigate associations between long-term HPA axis variation and individual acute stress reactivity, we tested 40 healthy volunteers for affective, endocrine, physiological, and neural reactions to a modified, compact version of the established in-MR stress paradigm ScanSTRESS (ScanSTRESS-C). Hair cortisol concentrations (HCC) served as an integrative marker of long-term HPA axis activity. First, the ScanSTRESS-C version proved to be valid in evoking a subjective, endocrine, physiological, and neural stress response with enhanced self-reported negative affect and cortisol levels, increased heart rate as well as increased activation in the anterior insula and the dorso-anterior cingulate cortex (dACC). Second and interestingly, results indicated a lower neuroendocrine stress response in individuals with higher HCC: HCC was negatively correlated with the area under the curve (respect to increase; AUCi) of saliva cortisol and with a stress-related increase in dACC activity. The present study explicitly targeted the relationship between HCC and acute stress reactivity on multiple response levels, i.e. subjective, endocrine and neural stress responses. The lower stress reactivity in individuals with higher HCC levels indicates the need for further research evaluating the role of long-term HPA axis alterations in the context of vulnerability or immunization against acute stress and following stress-related impairments.