Systematic review: The placebo effect of psychological interventions in the treatment of irritable bowel syndrome

Table 1 Descriptive statistics for characteristics of included studies

Ref.	Year	Country	n	Mean age (yr)	Female sex	Recruitment	Years of illness	Criteria	Therapy	Control	Format	Ses-sions	Trained therapist intervention/placebo	Protocol inter-vention/placebo
Craske et al[23] 2011	2011	United States	110	39.4	74	Community advertisement; university clinic		RII	Cognitive-behavior-al therapy	Psycho-educatio-nal support	Individual	10	Unclear/unclear	Yes/yes
Drossman et al[24] 2003	2003	United States and Canada	215	37.3	100	Community and hospital advertisement; physician referral in community or university-based practices		R1	Cognitive-behavior-al therapy	Psycho-educational support	Unclear	12	Yes/yes	Yes/yes
Gaylord et al[25] 2011	2011	United States	75	42.7	100	Local advertisement; physician care		RII	Mindful-ness	Support	Group	9	Yes/yes	Yes/yes
Moser et al[26] 2013	2013	Austria	100	45.5	79	Primary, secondary care and university clinic	4/10.5	RIII	Hypno-therapy	Support	Group	10	Yes/yes	Yes/no
Payne et al[27] 1995	1995	United States	34	40.1	85	Personal physician	16	RI	Cognitive therapy	Psycho-educatio-nal support	Therapy: individual; Control: group	10	Yes/unclear	Yes/yes
Shinozaki[28] 2010	2010	Japan	21	31.6	52	University clinic			Relax	Psycho-educatio-nal support	Individual	8	Yes/unclear	Yes/yes