Table 2.
Meta-analysis of the subgroups of the included studies
| Subgroups | Number of studies | Standardized mean difference (95% CI) | P-value |
|---|---|---|---|
| Type of Study | |||
| RCT | 9 | -1.70 (-2.97, -0.42) | < 0.001 |
| Crossover study | 2 | -1.55 (-2.10, -0.99) | 0.48 |
| Test of group differences: Qb (1) = 0.04, p = 0.83 | |||
| Pain assessment tool | |||
| VAS | 7 | -1.97 (-3.53, -0.41) | < 0.001 |
| NRS | 4 | -1.18 (-2.11, -0.25) | < 0.001 |
| Test of group differences: Qb (1) = 0.73, p = 0.39 | |||
| Number of tDCS sessions | |||
| 10 sessions | 4 | -2.87 (-5.29, -2.88) | < 0.001 |
| 8 sessions | 2 | -1.67 (-2.35, -0.98) | 0.16 |
| 5 sessions | 4 | -0.43 (-1.59, 0.74) | < 0.001 |
| 1 session | 2 | -0.74 (-2.69, 1.20) | < 0.001 |
| Test of group differences: Qb (3) = 5.22, p = 0.16 | |||
| Current intensity | |||
| 2 mA | 8 | -1.55 (-2.97, -0.13) | < 0.001 |
| Less than 2 mA | 3 | -1.88 (-2.67, -1.19) | 0.18 |
| Test of group differences: Qb (1) = 0.17, p = 0.68 | |||
| Electrode Position | |||
| M1 | 9 | -1.13 (-2.75, 0.49) | < 0.001 |
| DLPFC | 3 | -4.19 (-9.01, 0.63) | < 0.001 |
| Test of group differences: Qb (1) = 1.39, p = 0.24 | |||
| Sexuality | |||
| Only Female | 6 | -1.29 (-2.68, 0.10) | < 0.001 |
| Female & Male | 6 | -1.71 (-3.35, -0.08) | < 0.001 |
| Test of group differences: Qb (1) = 0.15, p = 0.70 | |||
Abbreviations: CI Confidence interval; RCT Randomized control trial, VAS Visual analogue scale, NRS Numeric rating scale, M1 Primary motor cortex, DLPFC Dorsolateral prefrontal cortex