Influence of chronic stress, discrimination and childhood adversity on the cortisol awakening response and acute stress response in Indigenous and non-Indigenous university students

Introduction: Indigenous peoples globally experience mental disorders at higher rates compared to the general population. Recently, alterations in neural stress processing have been studied as potential biological mechanisms underlying this health gradient. Here, we report on an integrative study of neuroendocrine regulation and stress processing and their psychosocial determinants. Methods: We recruited 26 individuals of Indigenous Australian ancestry and 26 non-Indigenous individuals matched for aged and gender from a university setting. We assessed cortisol awakening response (CAR) by collecting saliva samples across three weekdays. In a separate experiment, we tested neuroendocrine and autonomous reactivity to a psychosocial stress paradigm (Trier Social Stress Test, TSST) using salivary cortisol and heart rate variability (HRV). Chronic stress (K6, PSS), childhood adversity (MAES), racism (MIRE), and general psychopathology (HSCL) were assessed to test the relationship between these variables and neuroendocrine measures. Results: Relative to non-Indigenous participants, Indigenous participants had a flatter CAR. Interestingly, while in non-Indigenous participants chronic stress predicted a high CAR, the opposite relationship was found in Indigenous participants.We observed significantly lower time-domain measures of HRV in Indigenous participants. Frequency domain indices of HRV showed poorer recovery from stress in Indigenous participants, which was predicted by childhood adversity and internalized racism. Adverse childhood events were associated with blunted cortisol response to in the TSST in Indigenous participants. Conclusion: Altogether our results demonstrate differential HPA-axis regulation and autonomic response to acute psychosocial stress in a sample of Indigenous Australians. Psychosocial variables differentially affected HPAaxis and stress response in Indigenous and non-Indigenous participants