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

Table 2 Risk of bias ratings for included studies

Ref.	Year	Random sequence generation	Allocation concealment	Blinding of participants and personnel	Blinding of outcome assessment	Incomplete outcome data	Selective reporting	Dropout treatment/placebo control (%)	ITT or PP
Craske et al[23] 2011	2011	Low	Low	Low	Low	Low	Low	Interoceptive Exposure:34; Stress Management: 36/16	ITT
Drossman et al[24] 2003	2003	Low	Low	Low	Low	Low	Low	13/24	ITT
Gaylord et al[25] 2011	2011	Low	Low	Low	Low	Low	Low	6/18	ITT
Moser et al[26] 2013	2013	Low	Low	Low	Low	Low	Low	0/2	PP
Payne et al[27] 1995	1995	Unclear	Unclear	Low	Unclear	Low	Low	0/0	ITT
Shinozaki[28] 2010	2010	Unclear	Unclear	High	High	Low	Low	0/0	ITT

Possible ratings were low, high or unclear risk of bias. Studies with 2 control groups were rated twice for risk of bias because of lack of blinding (rated or active control groups appear in parentheses). ITT indicates that the analysis was intent-to-treat (analyzed as randomized). PP: Per protocol.