The human organism is in a state of dynamic equilibrium, homeostasis. The stress system is activated when homeostasis is challenged by extrinsic or intrinsic forces, the stressors. This system, whose central component is the central nervous system (CNS) and includes corticotropin-releasing hormone (CRH) and noradrenergic neurons, respectively, in the hypothalamus and the brain stem, has as its peripheral limbs the hypothalamic-pituitary-adrenal (HPA) axis and the autonomic (sympathetic) nervous system. Normal development and preservation of life and species are dependent on a normally functioning stress system. Maladaptive neuroendocrine responses, i.e., dysregulation of the stress system, may lead to disturbances in growth and development, and cause psychiatric, endocrine/metabolic, and/or autoimmune diseases or vulnerability to such diseases.