Table 3.
Results of meta-analyses of plasma and interstitial levels of endocannabinoids and N-acylethanolamines in patients with fibromyalgia syndrome and chronic widespread pain.
| Outcome | No. of reports | No. of subjects | SMD (95% CI) | P (overall effect) | Heterogeneity I2, χ2, P | |
|---|---|---|---|---|---|---|
| Case | Control | |||||
| Plasma AEA | ||||||
| FMS vs HC | 3 | 230 | 185 | −0.05 (−0.25, 0.15) | 0.61 | 0%, 1.77, 0.41 |
| Plasma 2-AG | ||||||
| FMS vs HC | 3 | 230 | 185 | 0.22 (−0.09, 0.53) | 0.16 | 52%, 4.20, 0.12 |
| Plasma PEA | ||||||
| FMS vs HC | 3 | 230 | 185 | 0.15 (−0.14, 0.44) | 0.31 | 46%, 3.73, 0.15 |
| CWP vs HC | 3 | 31 | 48 | 0.53 (0.01, 1.06) | 0.05 | 17%, 2.40, 0.30 |
| Total | 6 | 261 | 233 | 0.24 (−0.02, 0.51) | 0.07 | 37%, 7.98, 0.16 |
| Plasma OEA | ||||||
| FMS vs HC | 2 | 141 | 149 | 0.33 (0.10, 0.57) | 0.005 | 0%, 0.68, 0.41 |
| CWP vs HC | 3 | 31 | 48 | 0.44 (−0.47, 1.35) | 0.34 | 70%, 6.77, 0.03 |
| Total | 5 | 172 | 197 | 0.37 (0.00, 0.73) | 0.05 | 49%, 7.91, 0.09 |
| Plasma SEA | ||||||
| FMS vs HC | 2 | 141 | 149 | 0.52 (0.28, 0.75) | <0.0001 | 0%, 0.02, 0.90 |
| CWP vs HC | 3 | 31 | 48 | 0.31 (−0.15, 0.77) | 0.19 | 0%, 1.27, 0.53 |
| Total | 5 | 172 | 197 | 0.47 (0.27, 0.68) | <0.00001 | 0%, 1.90, 0.75 |
| Interstitial PEA | ||||||
| CWP vs HC | 2 | 35 | 43 | 0.26 (−0.19, 0.71) | 0.25 | 0%, 0.76, 0.38 |
| Interstitial SEA | ||||||
| CWP vs HC | 2 | 35 | 43 | 0.86 (0.33, 1.38) | 0.001 | 19%, 1.24, 0.27 |
Bold font indicates statistical significance (P ≤ 0.05).2-AG, 2-arachidonoylglycycerol; AEA, N-arachidonoylethanolamide or anandamide; CWP, chronic widespread pain; FMS, fibromyalgia syndrome; HCs, healthy controls; OEA, oleoylethanolamide; PEA, palmitoylethanolamide; SEA, stearoylethanolamide.