Individual reactivity and physiology of the stress response.

The biological response to stress involves the activation of two main neuroendocrine components, the hypothalamic-pituitary-adrenal axis and the sympathoadrenal medullary systems. Looking at the responses to stressors in a laboratory setting, e.g., cortisol production after exercising on a treadmill, is a valid and controlled way to study how people react to psychological and physical stressors. A common finding in such studies is that individuals respond bimodally to stress. More recently, researchers have been interested in the possible reasons why healthy individuals exhibit differential reactivity to stressors. The literature on the neuroendocrine responses to stress, with a particular focus on investigations of individual reactivity to psychological and physical stressors, is reviewed.