Ghodsi 2014.

Methods	RCT
Participants	Included: students with primary dysmenorrhoea and a pain score > 3 based on VAS, willing to take part in the study, aged between 18 to 23 years Excluded: mild dysmenorrhoea, student transferring to another university, unwilling to attend for the research, irregular uptake of capsules, any similar analgesic drug uptake, occurrence of unbearable side effects, and cases with the following diagnosis: pelvic inflammatory disease, endometriosis, and any pelvic tumour Age: mean age of fennel soft capsule group = 20.8 years, control group = 20.5 years Source: Islamic Azad University, Toyserkan Location: Iran
Interventions	Group 1: soft capsule fennel (30 mg) (every 4 hours, 3 days before menstruation until the 5th day and continued for 3 months) (N = 40) Group 2: no treatment (N = 40, 38 analysed)
Outcomes	Pain severity measured by VAS (scale 10 cm); self‐rated questionnaire, measured before fennel intake, and after 1, 2, and 3 months of use in 2 groups; nausea and weakness (VAS, 0 to 10 cm, 0 (no pain) to 10 (severe pain); self‐rated questionnaire); pain quality (McGill pain questionnaire (SF‐MPQ); self‐rated questionnaire) measured before fennel intake, and after 1 and 3 months of use; stress/worry about dysmenorrhoea (perceived stress scale; self‐rated questionnaire); levels of anxiety, stress, and well‐being (WELL being scale; self‐rated questionnaire).
Notes	We searched for more information regarding the McGill pain questionnaire. It consisted of 15 descriptors (11 sensory; 4 affective) which are rated on an intensity scale as: 0 = none, 1 = mild, 2 = moderate, or 3 = severe. (Scoring 0 to 45; 0 = no pain, 45 = severe pain)
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	“Students with primary dysmenorrhoea and pain scoring higher than 3, based on visual analog scales (VAS) entered the study and were divided randomly into 2 equal groups of intervention (n =40) and control (n=40).” Comment: the study authors did not describe the method of sequence generation.
Allocation concealment (selection bias)	Unclear risk	Comment: the study authors did not describe the method of allocation concealment.
Blinding (performance bias and detection bias) All outcomes	High risk	“The intervention group received 30 mg fennel capsules each 4 hours (8 am to 12 midnight) from about 3 days before menstruation till end of fifth day for 3 months. There was no treatment for control group and they did not receive any placebo.” Comment: it was not possible to blind the participant to treatment as the control group did not receive any treatment.
Incomplete outcome data (attrition bias) All outcomes	Low risk	“Two participants of the control group were excluded due to unwillingness to continue participation in the study, so the control group consisted of 38.” Comment: the dropout rate was 2.5% (2/80)).
Selective reporting (reporting bias)	Unclear risk	Comment: the study authors did not prespecify adverse event as an outcome. The study prespecified pain as an outcome but did not report any statistical data.
Other bias	Low risk	Comment: we did not identify any other potential sources of bias.