Longstreth 1981.

Methods	RCT
Participants	77 patients Setting unclear Mean age 38.4 years 83% female Mean duration of symptoms 7.9 years
Interventions	Bulking agent 8 weeks psyllium 19 g/day
Outcomes	Abdominal pain, continuous Global assessment, dichotomous
Notes	Unclear setting 2 weeks run‐in
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Not described
Allocation concealment (selection bias)	Low risk	Adequate
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Double‐blind, identical sachets
Incomplete outcome data (attrition bias) All outcomes	Low risk	Missing outcome data balanced in numbers across intervention groups with similar reasons for missing data across groups
Selective reporting (reporting bias)	Low risk	Expected outcomes were reported
Other bias	Low risk	The study appears to be free of other sources of bias