Do randomized clinical trials with inadequate blinding report enhanced placebo effects for intervention groups and nocebo effects for placebo groups?

Table 2 Enhanced placebo effects and nocebo effects

	IIEF-EF scores for placebo groups					IIEF-EF scores for intervention groups
ROB domain	No. of studies (no. of participants)*	Studies with low ROB (95% CI) (IV)	Studies with unclear or high ROB (95% CI) (IV)	Difference^a(95% CI)	Between MA-homogeneity Q (P value)	Studies with low ROB (95% CI) (IV)	Studies with unclear or high ROB (95% CI) (IV)	Difference^b(95% CI)
Summary 4 ROB-domains	5 (1,202)/16 (3,006)	1.92 (0.64 to 3.20)	1.56 (0.93 to 2.20)	0.33 (-0.96 to 1.62)	20 (0.48)	9.40 (6.96 to 11.83)	8.33 (7.29 to 9.37)	-1.0 (-1.35 to 3.47)
Allocation concealment	13 (2,487)/48 (11,169)	1.82 (1.14 to 2.50)	1.75 (1.37 to 2.12)	0.07 (-0.8 to 0.93)	58 (0.88)	9.10 (7.94 to 10.26)	8.34 (7.63 to 9.05)	0.78 (-0.65 to 2.20)
Blinding participant	42 (9,159)/19 (3,442)	1.88 (1.45 to 2.31)	1.43 (0.95 to 1.91)	0.42 (-0.33 to 1.16)	64 (0.35)	8.39 (7.69 to 9.10)	8.23 (7.28 to 9.19)	0.16 (-1.02 to1.33)
Blinding caregiver	17 (3,652)/42 (8,652)	1.94 (1.18 to 2.69)	1.77 (1.40 to 2.15)	0.17 (-0.61 to 0.96)	56 (0.54)	8.46 (6.92 to 10.01)	8.64 (8.15 to 9.13)	-0.25 (-1.50 to 1.00)
Blinding outcome assessor	17 (3,278)/42 (9,659)	1.82 (0.99 to 2.65)	1.84 (1.48 to 2.21)	-0.02 (-0.83 to 0.79)	57 (0.52)	8.59 (7.15 to 10.03)	8.43 (7.80 to 9.06)	0.15 (-1.12 to 1.41)

Impact of unblinding on summary changes from baseline International Index of Erectile Functioning-Erectile Functioning domain (IIEF-EF) scores with 95% CI with estimates of nocebo^a, enhanced placebo^b, placebo, and intervention effects. *Studies with low risk of bias (ROB) versus studies with unclear or high ROB. MA: Meta-Analysis, Q: Cochran’s Q, IV; Inverse Variance.

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