Table 2.

Characteristics and results of the studies reviewed.

Ref.	Demographics	Objectives	Intervention	Outcome Measures	Results (p Values)
[35]	FM: n = 29 52.1 ± 8.9 years BMI 27.1 ± 5.9 Control: n = 29 52.7 ± 8.4 years BMI 25.0 ± 3.5	To determine salivary cortisol and pain levels in different conditions such as stress, upon awakening, 30 min, 60 min after awakening, etc.	Collection of saliva eight times at the time points: arrival at the hospital (4:45 pm), late afternoon, late evening, CAR and after leaving the hospital the next day (5:05 pm)	-Salivary cortisol -Pain (VAS)	Patients in FM showed declining cortisol levels over the day, most pronounced in the morning (CAR). Cortisol levels lower in FM versus Control. Differences significant between groups in 1st, 2nd, 5th and 8th measurement (p = 0.010, p = 0.035, p = 0.001 and p = 0.050 respectively) Difference between groups in pain perception
[31]	FM: n = 17 53 ± 7.98 (42–69 years) Control: n = 19 53.32 ± 6.46 years	To examine changes produced in cortisol and their correlation with pain, depression and quality of life in postmenopausal women with fibromyalgia	Blood cortisol measured after 8 h of sleep along with pain threshold and pain tolerance	-Cortisol levels measured over three alternate days -Algometry post blood collection on 18 Tender Points (TPs) (kg/cm2) until participant reports “starting to feel pain” and “can’t take it anymore”	Pain threshold p > 0.0001 between groups Pain tolerance p > 0.0001 between groups α = 5% Significant difference between groups No link between cortisol levels and pain threshold or tolerance
[33]	FM: n = 12 50 ± 2.07 years BMI 26.30 ± 0.363 Control: n = 15 41 ± 2.98 years BMI 26.47 ± 1.01	To determine cortisol and IL-6 responses after measuring PPT at TPs	4-day study: measurements at baseline and after low dose overnight dexamethasone (0.5 mg)	-Blood cortisol -PPT -TP count	Cortisol levels significantly increased post PPT measurement p < 0.04 PPT measurement led to higher pain levels when measures were analyzed post hoc
[30]	FM: n = 19 51 (25–64 years) BMI 27.1 Control: n = 20 48 (36–54 years) BMI 26.5	To assess the effects of balneotherapy on the hypothalamic-pituitary axis	3-week balneotherapy program consisting 20-min sessions 5 days/week	-Blood cortisol (g/dL) Pre/Post intervention -TP count	Cortisol levels fell (p = 0.002) after the Week 3 balneotherapy session compared to baseline levels on Day 1 in controls. Cortisol levels rose by 19% in the Week 3 session compared to Day 1 in the FM group (p = 0.005), and fell by 20% in the control group. TP count fell by 7% (p = 0.02) in FM
[40]	FM: n = 20 52.0 ± 1.4 years Control: n = 16 4852.2 ± 1.5 years	To determine cortisol levels associated with pain following an exhaustive exercise test	Fasting treadmill exercise to V02 peak of some 20 min duration	-Blood cortisol -PTT	PPT reduced in FM (p = 0.001) No significant differences in cortisol pre and post exercise (p = 0.10)
[18]	FM1: n = 25 36.9 years FM2: n = 25 35.1 years	To assess pain and blood cortisol levels following a home stretching and aerobic exercise program	6 weeks of home exercise or 6 weeks home + aerobic exercise	-Blood cortisol -PTT -TP count	Pain reductions observed in FMI (p < 0.025) and FM 2 (p < 0.001) TP count reduced Significant differences in cortisol levels from baseline to first and second measurement (p = 0.014) Post-hoc contrast statistic increased from 1st to 2nd measurement
[32]	FM: n = 14 51.07 ± 12.38 years BMI 23.65 ± 4.00 TPs 17.10 ± 0.05	To examine the effects of functional respiratory training on pain and their correlation with cortisol levels	Diaphragm breathing exercise intervention. Measurements made over 12 weeks: first 4 weeks control followed by 8 weeks of exercise.	-Sleep quality -Algometry pain tolerance threshold (PTT) -Urine cortisol	Significant increases produced in PTT between week 4 and 12 (p < 0.05) in occiput, low cervical and 2nd rib No changes in cortisol levels during intervention
[34]	FM: n = 21 51.43 ± 11.26 years BMI 26.51 ± 5.18 Control: n = 23 48.26 ± 11.03 years BMI 26.82 ± 4.22	To assess salivary cortisol, pain (FIQ) and TPs	Health Education program	-Salivary cortisol -Pain (FIQ) -TP count	Cortisol levels rose in FM (p = 0.02), but not in Control. Pain scores improved in FM (p < 0.02) but remained the same in Control
[36]	FM: n = 24 45.9 ± 2.89 years BMI 26.04 ± 2.52	To determine salivary cortisol levels and pain after a 3-month Swedish massage program	Massage program = 24 × 40 min sessions (2 afternoon sessions/week)	-Salivary cortisol -Pain (FIQ)	No significant differences before and after the 3- month intervention. Pre- post intervention differences significant for first session and first month (p < 0.001), but significance lost after 2nd and 3rd month
[38]	FM: n = 31 57 ± 8 years BMI 28.4 ± 5.7 Control: n = 23 57 ± 10 years BMI 27.4 ± 5.4	To correlate chronic pain with morning blood cortisol levels and leg pain	Comparative study	-Blood cortisol -Pain (VAS)	Differences significant between groups in cortisol levels (p = 0.01) and pain perception (p < 0.001)

BMI: body mass index; FM: fibromyalgia; TP: tender points; VAS: visual analogic scale; FIQ: fibromyalgia impact questionnaire; PTT: pain tolerance threshold; PPT: pressure pain threshold.