Psychobiological responses in women with regional or widespread musculoskeletal pain conditions

Abstract: Musculoskeletal disorders (MSDs) are very common. Regional chronic shoulder and neck pain (SNP) and widespread chronic pain due to fibromyalgia syndrome (FMS) are examples of MSDs characterized by altered physiology of the autonomic nervous system (ANS) and the hypothalamic-pituitary-adrenal (HPA) axis. The aims of this thesis are to compare the cortisol awakening response (CAR) in SNP women, FMS patients and healthy controls, and to compare salivary cortisol levels, urinary catecholamine levels (adrenaline, noradrenaline, and dopamine), and cardiovascular responses in FMS patients and healthy controls. Self-ratings of sleep, anxiety, perceived stress, and pain were also investigated. In Study I, CAR tended to be higher in SNP women than in healthy controls, whereas it was significantly higher than in FMS patients. Moreover, CAR was significantly lower in FMS patients than in healthy controls. Study II showed that cortisol levels were lower in FMS patients than in healthy controls during the rest of the day as well. In Study III, adrenaline and dopamine (but not noradrenaline) levels were significantly lower in FMS patients than in healthy controls. Resting heart rate was significantly higher in FMS patients than in healthy controls, but no differences emerged during stress provocation or unconstrained daily activities. Finally, SNP women and FMS patients reported more pain and health complaints than did healthy controls, but SNP women were less affected. Potential confounders (e.g., age, obesity, physical exercise) had no effects on the findings. Taken together, the findings show altered ANS and HPA axis regulation in FMS patients. Specifically, the hyperactive HPA axis found in SNP women (i.e., higher cortisol levels) might constitute a preliminary stage of a hypoactive HPA axis in FMS patients (i.e., lower cortisol levels). In view of this, an altered regulation of the HPA axis in the progression from regional to widespread MSDs may follow a temporal development.