Habituation of the biological response to repeated psychosocial stress: a systematic review and meta-analysis.

Recurrent psychosocial stress poses a significant health challenge, prompting research into mechanisms of successful adaptation. Physiological habituation, defined as decreased reactivity to repeated stressors, is pivotal in protecting the organism from allostatic load. Here, we systematically review and meta-analyze data from studies investigating the capacity of central stress systems to habituate when repeatedly exposed to a standardized psychosocial stressor, the Trier Social Stress Test (k=47). For a comprehensive overview of biological stress systems, we examine multiple markers of the hypothalamic-pituitary-adrenal (HPA) axis, the autonomic nervous system (ANS), and the immune system. Our findings indicate that habituation patterns vary substantially between different stress systems. While most studies provide robust evidence for rapid and substantial HPA-axis habituation, ANS and immune marker responses to repeated stress are less uniform. We further integrate existing knowledge on personal and environmental influences contributing to individual differences in habituation capacity. Additionally, we discuss the implications of stress habituation patterns for health outcomes and the design of longitudinal stress studies and highlight potential avenues for future research.