Table 2.

Characteristics of studies included in the verbal suggestion (pain) meta-analysis.

Author	Year	N	Sample age	Percent female	Sensation induction method	Placebo manipulation	Rating scale	Risk of bias score	Comparison	Outlier based on funnel plot
Aslaksen4	2008	63	24.2	51%	Thermal	Inert pill	0-100 VAS	0	W
Aslaksen6	2015	48	23.4	51%	Thermal	Inert gel	0-100 VAS	3	B
Aslaksen3	2016	32	21.6	54%	Thermal	Inert gel	0-100 VAS	3	B
Brown17	2013	61	19.5	59%	Cold pressor	Inert gel	0-10 NRS	5	W
Camerone19	2021	21	22.0	52%	Electrical	Inert gel	0-10 NRS	4	W
Colloca34	2008	14	22.3	100%	Electrical	Sham electrode	0-10 NRS	3	W
Colloca35	2008a	16	32.0	66%	Laser	Inert gel	0-10 NRS	5	W
Colloca31	2009	16	22.6	100%	Electrical	Sham electrode	0-10 NRS	5	W
Colloca36	2019	107	28.1	64%	Electrical	Sham electrode	0-100 NRS	3	W
De Pascalis41	2017	55	23.4	100%	Cold cup	Inert gel	0-100 NRS	3	W
De Pascalis42	2019	58	24.5	100%	Cold cup	Inert gel	0-100 pain intensity scale	1	W
Disley45	2021	50	21.0	87%	Cold pressor	Inert nasal spray	−5 to +5 VAS	1	W
Ellingsen51	2013	28	25.5	33%	Thermal	Inert nasal spray	0-100 NRS	4	W	+
Fehse54	2015	27	32.0	0%	Thermal	Inert pill	0-10 pain intensity scale	5	B
Geers61	2014	106	19.6	67%	Cold pressor	Inert gel	0-100 VAS	5	W
Gniß65	2020	32	21.0	50%	Thermal	Inert gel	0-100 VAS	2	W
Horing73	2020	17	19.6	54%	Thermal	Inert pill	0-10 VAS	2	W
Hunter75	2014	15	27.0	100%	Electrical	Sham electrode	0-10 VAS	3	W
Johnson78	1997	24	NR	50%	Cold pressor	Sham TENS	0-100 VAS	2	W
Kube84	2020	25	23.6	44%	Thermal	Inert gel	0-100 VAS	2	W
Locher88	2017	37	26.6	62%	Thermal	Inert gel	0-100 VAS	6	W
Lyby90	2010	63	NR	48%	Thermal	Inert pill	0-100 VAS	2	W
Lyby91	2011	33	22.0	51%	Thermal	Inert gel	0-10 NRS	1	W
Lyby92	2012	33	22.0	30%	Thermal	Inert pill	0-10 NRS	2	W
Matre97	2006	18	NR	41%	Thermal	Sham magnets	0-100 VAS	6	W
Milling101	2009	41	NR	63%	Pressure	Inert gel	0-30 pain intensity scale	4	W
Montgomery103	1996	56	NR	57%	Pressure	Inert gel	0-10 pain intensity scale	10	W
Nemoto107	2007	10	NR	50%	Laser	Inert pill	0-10 pain intensity scale	3	W
Nir108	2012	24	25.8	0%	Hot water	Inert pill	0-100 NRS	3	B
Peerdeman112	2015	59	21.8	71%	Cold pressor	Inert pill	0-10 NRS	3	B
Petrovic115	2002	9	NR	NR	Thermal	Inert pill	0-100 VAS	6	W
Pontén116	2019	15	27	60%	Thermal	Sham electrode	0-100 NRS	2	W
Rhudy120	2018	33	35.3	51%	Electrical	Inert gel	0-100 VAS	6	W
Roelofs121	2000	30	21.6	0%	Electrical	Sham IV	0-100 VAS	5	B
Rose122	2012	41	NR	61%	Cold pressor	Inert gel	0-10 VAS	6	B
Skvortsova133	2018	54	22.1	100%	Cold pressor	Inert nasal spray	0-10 NRS	0	B
Valentini140	2018	39	24.9	54%	Laser	Inert gel	0-10 NRS	2	B
van Laarhoven145	2011	33	21.8	100%	Histamine	Inert gel	0-100 VAS	1	W
Yeung153	2020	60	24.5	72%	Cold pressor	Inert gel	0-10 VAS	4	B

For studies using a within-subject comparison to measure the placebo effect, N is reported as the number of participants from the group in which the comparison was made. For studies using a between-subject comparison, N is reported as the number of participants from the placebo and control groups from which the comparison was made or only the placebo condition in the case of within-subject comparisons.

C, control; IV, intravenous; N, sample size; NR, not reported; NRS, numeric rating scale; P, placebo; TENS, transcutaneous electric nerve stimulation; VAS, visual analogue scale.