Fibromyalgia syndrome (FM) is a chronic pain syndrome that was defined by the American College of Rheumatology (ACR) in 1990 as widespread pain for more than 3 months and the presence of at least 11 out of 18 tender points [1]. The tenderness of FM patients is associated with increased peripheral and/or central nervous system (CNS) responsiveness to peripheral stimuli that can be either noxious (hyperalgesia) or non-noxious (allodynia). In 2010, the ACR endorsed the “Preliminary Diagnostic Criteria for FM”, which shifted the focus from quantitative sensory testing, i.e. tender points, to self-reported symptoms including fatigue, waking up unrefreshed, cognitive dysfunction, and somatic symptoms [2]. Currently a vigorous debate is ongoing as to whether defining FM as a completely self-reported syndrome represents a significant improvement over the 1990 Criteria [3]. The prevalence of FM in the US is estimated to be 3.4% in women and 0.5% in men and is reported to be high in individuals with other rheumatic conditions, including systemic lupus erythematosus or Sjögren’s syndrome. Additionally, almost all FM patients complain of disturbed sleep, distress, and pronounced fatigue. FM represents the extreme end of the spectrum of chronic wide-spread pain syndromes in the general population and is an illness that disproportionably affects women (the ratio of women to men affected is approximately 6:1 [4,5]). FM shows considerable overlap with other chronic pain syndromes, such as irritable bowel syndrome, chronic fatigue syndrome, migraine, and temporomandibular disorder. Like many other chronic pain syndromes FM has no single specific feature, but represents a symptom complex of self-reported or elicited findings.