Table 3.
Descriptive statistics (second and fourth columns) and multiple linear regression modeling results (sixth column) showing changes in outcome variables as a function of stimulation (active vs sham tDCS) over time
| Score and No., Mean (SD) [Range] |
P | ||||
|---|---|---|---|---|---|
| Active tDCS | No. | Sham tDCS | No. | ||
| DVPRS | |||||
| Day 1 | 5.4 (2.2) [1–9] | 10 | 5.5 (1.1) [4–7] | 11 | 0.97 |
| Day 5 | 4.8 (2.7) [0–8] | 10 | 4.6 (2.3) [1–8] | 11 | 0.82 |
| Day 10 | 4.0 (2.4) [0–8] | 10 | 4.0 (2.2) [1–8] | 11 | 0.91 |
| 6-wk follow-up | 4.3 (2.5) [0–9] | 10 | 4.8 (1.8) [2–8] | 10 | 0.58 |
| WHY-MPI-C | |||||
| Day 1 | 31.3 (16.1) [9–53] | 10 | 36.9 (13.3) [14–60] | 11 | 0.45 |
| Day 5 | 39.9 (23.0) [9–85] | 10 | 40.8 (18.9) [8–82] | 11 | 0.41 |
| Day 10 | 41.6 (21.9) [12–78] | 10 | 41.0 (15.8) [15–68] | 11 | 0.26 |
| 6-wk follow-up | 48.4 (21.2) [15–85] | 10 | 35.3 (17.7) [11–73] | 10 | 0.002* |
| RMDQ | |||||
| Day 1 | 13.8 (5.4) [5–20] | 10 | 12.5 (4.9) [3–19] | 11 | 0.46 |
| Day 5 | 13.2 (6.0) [1–20] | 10 | 12.5 (5.3) [2–21] | 11 | 0.54 |
| Day 10 | 12.5 (5.6) [0–19] | 10 | 12.8 (4.1) [4–18] | 11 | 0.13 |
| 6-wk follow-up | 12.7 (5.6) [1–20] | 10 | 15.4 (5.5) [3–22] | 10 | 0.001* |
| CPAQ-8 | |||||
| Day 1 | 31.0 (7.2) [22–42] | 6 | 29.9 (10.5) [10–48] | 9 | 0.98 |
| Day 5 | 29.8 (5.2) [22–36] | 5 | 27.9 (5.6) [15–35] | 9 | 0.52 |
| Day 10 | 30.5 (4.6) [23–36] | 6 | 28.6 (8.4) [14–45] | 9 | 0.74 |
| 6-wk follow-up | 32.5 (5.5) [26–42] | 6 | 27.9 (8.6) [14–39] | 8 | 0.40 |
| PHQ-9 | |||||
| Day 1 | 11.0 (7.8) [3–22] | 10 | 8.1 (5.2) [0–14] | 10 | 0.27 |
| Day 5 | 10.0 (8.3) [0–22] | 10 | 7.0 (4.7) [0–14] | 11 | 0.89 |
| Day 10 | 8.9 (7.1) [2–20] | 10 | 6.8 (4.9) [0–15] | 11 | 0.65 |
| 6-wk follow-up | 7.4 (6.1) [1–17] | 10 | 8.9 (6.0) [0–17] | 10 | 0.003* |
| GAD-7 | |||||
| Day 1 | 7.5 (7.6) [0–19] | 10 | 8.3 (5.2) [0–14] | 11 | 0.77 |
| Day 5 | 7.2 (7.4) [0–18] | 10 | 6.2 (5.9) [0–18] | 11 | 0.31 |
| Day 10 | 6.2 (6.7) [0–18] | 10 | 7.0 (6.3) [0–17] | 11 | 0.96 |
| 6-wk follow-up | 6.0 (6.6) [0–17] | 10 | 4.9 (4.5) [0–13] | 10 | 0.32 |
| PASS-20 | |||||
| Day 1 | 34.4 (22.8) [6–80] | 10 | 37.5 (25.3) [4–74] | 11 | 0.75 |
| Day 5 | 34.9 (23.5) [2–78] | 10 | 30.4 (21.2) [2–71] | 11 | 0.27 |
| Day 10 | 27.8 (24.2) [0–72] | 9 | 27.4 (21.3) [1–58] | 11 | 0.67 |
| 6-wk follow-up | 26.3 (23.6) [0–59] | 10 | 26.4 (22.0) [1–71] | 10 | 0.67 |
| CEQ | |||||
| Day 1 | 35.9 (7.8) [25.2–51.6] | 10 | 38.5 (7.6) [29.6–53.2] | 11 | 0.49 |
| Day 10 | 38.8 (9.7) [23.6–54.0] | 9 | 33.7 (9.0) [22.0–51.6] | 10 | 0.038* |
| CSQ-8 | |||||
| Day 1 | 29.5 (3.3) [21–32] | 10 | 29.2 (2.4) [25–32] | 11 | 0.83 |
| Day 10 | 29.3 (2.2) [25–32] | 10 | 28.3 (2.9) [24–32] | 11 | 0.57 |
All assessments except for CSQ-8 were administered in person at the start of an experimental session before commencing tDCS; CSQ-8 was administered immediately after tDCS finished. Day 1 assessment scores were therefore considered baseline values for the purposes of this study. Statistical significance was defined as the traditional two-tailed P ≤ 0.05. WHY-MPI-C General Activity Subscale, RMDQ, PHQ-9, and CEQ all showed significant improvements at the six-week follow-up telephone assessment, which occurred on average 6.2 weeks after the day 10 tDCS session (tDCS sessions occurred only on weekdays); one PVAMC participant was lost to 6-week follow-up. The third and fifth columns report the No. of participants included in the model for a particular condition and measure at a given time point. Differences from the last column of Table 2 are due to CPAQ-8 not being obtained in all participants, the participant lost to follow-up, and missed/incomplete measures from other participants. See the Methods for how missing data were handled. CEQ is provided as a total score that could range from 6 to 54; see the text for full details of how this was calculated. For simplicity, DVPRS is reported only for the following time points: day 1, day 5, day 10, and 6-week follow-up.
CEQ = Credibility/Expectancy Questionnaire; CPAQ-8 = Chronic Pain Acceptance Questionnaire; CSQ-8 = Client Satisfaction Questionnaire-8; DVPRS = Defense and Veterans Pain Rating Scale; GAD-7 = Generalized Anxiety Disorder scale; PASS-20 = Pain Anxiety Symptoms Scale; PHQ-9 = Patient Health Questionnaire; RMDQ = Roland Morris Disability Questionnaire; tDCS = transcranial direct current stimulation; WHY-MPI-C = West Haven-Yale Multidimensional Pain Inventory’s General Activity Subscale.