Transitioning from acute to chronic stress is defined by the duration and intensity of the activation of the HPA axis (hypothalamic-pituitary-adrenal axis). In an acute response, cortisol levels spike to manage immediate threats and then return to baseline once the threat passes. Chronic stress occurs when this feedback loop fails to reset, leading to sustained high levels of glucocorticoids.
Key biological markers include dysregulated cortisol rhythms. While acute stress involves a sharp morning peak, chronic stress often results in a flattened diurnal cortisol slope, where levels remain abnormally high in the evening or drop too low in the morning. Other markers include elevated C-reactive protein (CRP), which indicates systemic inflammation, and persistent elevation of adrenaline (epinephrine) and noradrenaline.
Physiological thresholds are often measured through Heart Rate Variability (HRV). A significant and sustained decrease in HRV indicates a loss of autonomic nervous system flexibility, signaling that the body is stuck in a sympathetic dominant state. When these markers—cortisol dysregulation, systemic inflammation, and low HRV—persist over weeks or months, the body has transitioned into a chronic stress state.
