Table 1.

Concurrent and remembered placebo effects and correlations between expected relief and concurrent and remembered pain reductions across groups and placebo tests

	n	Concurrent analgesia, Cohen's d (CI)	Remembered analgesia, Cohen's d (CI)	Expected × concurrent; Pearson's r	Expected × remembered;Pearson's r
Pain intensity
Group 1 (overnight delay; morning test)	12	1.16 (0.29–2.02)	1.17 (0.31–2.04)	0.88***	0.86***
Group 2 (daytime delay; evening test)	13	0.93 (0.12–1.74)	1.34 (0.49–2.19)	0.61*	0.66*
Group 3, test 1 (no delay; evening test)	13	0.80 (0.00–1.60)	0.89 (0.08–1.69)	0.49†	0.12
Group 3, Test 2 (overnight delay; morning test)	13	0.65 (−0.14 to 1.43)	0.54 (−0.24 to 1.32)	−0.23	−0.43
Pain unpleasantness
Group 1 (overnight delay; morning test)	12	0.95 (0.11–1.80)	0.93 (0.09–1.77)	0.83***	0.87***
Group 2 (daytime delay; evening test)	13	0.89 (0.08–1.69)	1.29 (0.45–2.14)	0.68**	0.78**
Group 3, test 1 (no delay; evening test)	13	0.57 (−0.21 to 1.36)	1.30 (0.45–2.14)	0.31	0.05
Group 3, test 2 (overnight delay; morning test)	13	0.54 (−0.24 to 1.32)	0.41 (−0.36 to 1.19)	−0.35	−0.49†

Cohen's d with Hedges-bias correction was used to evaluate effect size, and Pearson's correlation coefficients (r) were established between expected, concurrent, and remembered analgesia scores. Analgesia scores correspond to the difference between pain ratings at the control and placebo stimulation sites. CI, Confidence interval.

*p < 0.05,

**p < 0.01,

***p < 0.001,

^†p = 0.09.