Psychophysiological responses during pain and pain plus placebo conditions, all subjects
| Pain | Pain + Plbo | t | p | |
|---|---|---|---|---|
| Measure | ||||
| Mean q 15 s momentary VAS intensity | 28.3 ± 13.1 | 24.0 ± 13.5 | 2.01 | 0.03 |
| Volume 5% intramuscular saline (μl) | 2796 ± 956 | 3025 ± 100 | 1.10 | 0.14 |
| VAS overall intensity | 37.5 ± 19.9 | 27.4 ± 15.7 | 3.40 | 0.002 |
| VAS overall unpleasantness | 40.4 ± 25.5 | 32.9 ± 21.6 | 2.05 | 0.03 |
| MPQ sensory subscale | 14.3 ± 4.5 | 13.7 ± 5.4 | 0.44 | 0.33 |
| MPQ affective subscale | 0.9 ± 1.0 | 0.4 ± 0.6 | 2.83 | 0.007 |
| MPQ total | 19.4 ± 5.5 | 18.5 ± 7.4 | 0.40 | 0.35 |
| PANAS negative affect | 2.1 ± 2.1 | 2.6 ± 3.5 | 0.97 | 0.44 |
| PANAS positive affect | 13.4 ± 7.4 | 14.1 ± 6.1 | 0.87 | 0.20 |
| POMS-TMD score | 9.7 ± 7.9 | 10.7 ± 9.5 | 0.99 | 0.17 |
| Rating to stimulus (milliliters of algesic substance required) ratio | ||||
| Mean q 15 s momentary VAS intensity | 14.7 ± 16.1 | 10.8 ± 1.0 | 1.40 | 0.09 |
| VAS overall intensity | 19.5 ± 21.5 | 12.3 ± 11.4 | 1.98 | 0.03 |
| VAS overall unpleasantness | 18.5 ± 18.6 | 13.2 ± 10.6 | 1.76 | 0.05 |
| MPQ sensory subscale | 6.0 ± 3.3 | 5.5 ± 4.4 | 0.43 | 0.38 |
| MPQ affective subscale | 0.5 ± 0.6 | 0.2 ± 0.4 | 2.32 | 0.02 |
| MPQ total | 8.4 ± 5.1 | 7.6 ± 6.6 | 0.41 | 0.34 |
| PANAS negative affect | 0.8 ± 1.0 | 1.5 ± 2.9 | 0.97 | 0.17 |
| PANAS positive affect | 5.8 ± 4.6 | 5.7 ± 4.4 | 0.15 | 0.44 |
| POMS-TMD score | 4.7 ± 4.6 | 5.3 ± 6.2 | 0.36 | 0.37 |
Mean ± 1 SD of psychophysical measures of pain during the sustained pain challenge in the absence (Pain) and presence (Pain + Plbo) of placebo in 14 males 20-30 years of age. Mean q 15 s momentary VAS intensity refers to the average ratings of momentary pain acquired every 15 s for the duration of the pain challenge (20 min). Volume 5% intramuscular saline (in microliters) is the total volume of algesic substance introduced by the adaptive pain control system to maintain pain. The remainder of the scales (VAS, 0-100 of overall pain intensity and unpleasantness; MPQ; PANAS; and POMS-TMD) were obtained immediately after completion of the pain challenge. Data are also expressed as the relationship between the subject's ratings and the stimulus needed to maintain pain during the experimental period [rating to stimulus (in milliliters) ratio]. These ratios are used as the subjective assessment of placebo effects. Paired, one-tailed t test, p < 0.05.