**1. Introduction**

186 Psoriasis

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in the squirrel monkey. J Invest Dermatol 1968, 51:120-136

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579

1980;5:528-536

psoriasis. J Dermatol 1998;25:231-233

from the literature including a series of 6 new cases. Am J Clin Dermatol 2008;9:1-

Nowadays stress is a normal part of everyday living and the physiological and behavioral consequences of exposure to stressful situations have been extensively studied for decades. The neuroendocrine stress response is a necessary mechanism but disrupts homeostatic process and it is subserved by a complex system located in both the central nervous system (CNS) and the periphery. Stressor-induced activation of the hypothalamus–pituitary– adrenal (HPA) axis and the sympathetic nervous system (SNS) results in a series of neural and endocrine adaptations known as the "stress response" or "stress cascade." The stress cascade is responsible for allowing the body to make the necessary physiological and metabolic changes required to cope with the demands of a homeostatic challenge. In recent years, evidence has suggested that stress responses are not only under control of the CNS but are influenced by peripheral tissue, outside of the classical HPA axis. Corticotrophinreleasing hormone (CRH) is a central component of the HPA axis and is an important coordinator of the systemic stress response with subsequent modulation of the inflammatory response. In peripheral sites, cutaneous CRH and CRH-receptor1 (CRH-R1) is believed to regulate various functions of the skin that are important for local homeostasis. Common inflammatory skin disorders such as atopic dermatitis and psoriasis exhibit decreased barrier function and recent studies suggest that the complex response of epidermal cells to barrier disruption may aggravate, maintain, or even initiate such conditions.
