Volz 2016

Methods	Parallel RCT
Participants	Country of study: Germany Setting: laboratory Condition: chronic abdominal pain with inflammatory bowel disease Prior management details: participants allowed to continue anti‐inflammatory drugs and acute pain medication n = 20 Age, mean (SD) active group 40.6 (12.5) years, sham group 34.4 (13.2) years Duration of symptoms: active group 10 (8.9) years, sham group 34.4 (13.2) Gender distribution: 13 F, 7 M
Interventions	Stimulation type: tDCS Stimulation parameters: intensity 2 mA, 35 cm2 electrodes, duration 20 min Stimulation location: anode M1 contralateral to painful side, cathode supraorbital area, contralateral to anode Number of treatments: x 1 daIly for 5 days Control type: sham tDCS
Outcomes	Primary: pain VAS, anchors 0 = no pain, 10 = the worst pain possible When taken: postintervention, 1 week postintervention Secondary: inflammatory bowel disease QoL questionnaire AEs
Notes	COI: study authors declared no COI Sources of support: "This study has been supported by the grant “Patientenorientierte Forschung bei CED 2014” of the “Deutsche Morbus Crohn/Colitis ulcerosa Vereinigung e.V.” (Not industry)
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: “Randomization was performed by the unblinded researcher (A.F.) in blocks of 4 generated from a computer‐based random allocation.”
Allocation concealment (selection bias)	Unclear risk	Quote: “Quote: “Randomization was performed by the unblinded researcher (A.F.)” Comment: no apparent steps to conceal allocation
Adequate blinding of participants?	Unclear risk	Evidence that assessor blinding can be inadequate at intensity of 2 mA. No formal assessment of blinding success
Adequate blinding of assessors?	Unclear risk	Evidence that assessor blinding can be inadequate at intensity of 2 mA. No formal assessment of blinding success
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Comment: levels of dropout, if any, not reported
Selective reporting (reporting bias)	Low risk	Comment: outcomes reported adequately
Study Size	High risk	Comment: n = 20
Study duration	High risk	Comment: 1‐week postintervention maximum follow‐up.
Other bias	Low risk	Comment: no further bias detected