Vahedi 2008.

Methods	RCT
Participants	50 diarrhoea‐predominant IBS patients Tertiary GI clinic Rome II criteria Mean age 36 years 42% female Mean duration of symptoms 39 months
Interventions	Antidepressant amitriptyline 10 mg for 2 months
Outcomes	Abdominal pain, dichotomous IBS‐symptom score, continuous and dichotomous
Notes	No run‐in Only diarrhoea‐predominant IBS
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Computer‐generated
Allocation concealment (selection bias)	Low risk	Adequate
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Double‐blind, identical placebo. Both patients and researchers were unaware of the true identity of the prescribed medicine
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