Idiopathic pain disorders--pathways of vulnerability.

Idiopathic pain disorders (IPDs) consist of such conditions as temporomandibular joint disorders (TMJD), fibromyalgia syndrome (FMS), irritable bowel syndrome (IBS), chronic headaches, interstitial cystitis, chronic pelvic pain, chronic tinnitus, whiplash-associated disorders, and vulvar vestibulitis (VVS). IPDs commonly aggregate as ‘‘comorbid’’ conditions that are characterized by a complaint of pain as well as a mosaic of abnormalities in motor function, autonomic balance, neuroendocrine function, and sleep. Although the mechanisms that underlie the majority of these conditions are poorly understood, IPDs have been associated with a state of pain amplification and psychological distress (McBeth et al., 2001; Bradley and McKendree-Smith, 2002; Verne and Price, 2002; Gracely et al., 2004).