• Pain processing is complex and involves nociception, transmission, modulation, and perception. • Objective examination using function neuroimaging has demonstrated that pain in patients with fibromyalgia syndrome (FMS) is ‘real’. • Physiological pain is important in protecting us from harm, while maladaptive (pathologic) pain injury is caused by functional abnormality of the nervous system. FMS is characterized by maladaptive pain. • Sleep study in patients with FMS has confirmed reduced deep quality and increased wakefulness. In healthy volunteers, selective deprivation of non-REM sleep...

• Pain processing is complex and involves nociception, transmission, modulation, and perception. • Objective examination using function neuroimaging has demonstrated that pain in patients with fibromyalgia syndrome (FMS) is ‘real’. • Physiological pain is important in protecting us from harm, while maladaptive (pathologic) pain injury is caused by functional abnormality of the nervous system. FMS is characterized by maladaptive pain. • Sleep study in patients with FMS has confirmed reduced deep quality and increased wakefulness. In healthy volunteers, selective deprivation of non-REM sleep can induce symptoms and hyperalgesic tender sites of FMS. • Patients with FMS often report experiencing previous stressful or traumatic events. A reduced HPA axis response to stress can contribute to development or worsening of FMS.