Stress as a Pathophysiological Factor in Functional Somatic Syndromes

Functional somatic syndromes (FSS) are defined by a constellation of symptoms for which after thorough medical examination no structural pathology and no proportional tissue abnormalities can be identified. Pathophysiology of these syndromes has remained elusive and treatment options are limited. Current research efforts acknowledge the importance of stress as a potential risk factor in the manifestation and maintenance of FSS. A substantial body of research has focused on psychological stress factors as well as alterations of the endocrine stress system (the hypothalamicpituitary- adrenal, HPA axis, in particular), the immune system, and the autonomic nervous system (ANS). Dysregulation of these systems might explain some of the symptoms of FSS. In this review, we describe studies reporting stress-related findings in three of the most prevalent and well-described FSS, i.e. chronic fatigue syndrome (CFS), irritable bowel syndrome (IBS), and fibromyalgia syndrome (FMS). Psychobiological processes which seem to play a role in the translation of stress into functional symptoms and syndromes are discussed.