Hosseinlou 2014.

Methods	RCT
Participants	Included: women 13 to 18 years of age, single, suffering from dysmenorrhoea, with regular menstrual cycles, no other health problems (according to their medical history), and low dietary fish intake (not more than once per week). Excluded: no information Age: no information Source: high school female students in Urmia city Location: Iran
Interventions	Group 1: vitamin B1 tablet (100 mg/day) (N = 60) Group 2: fish oil pearl capsule (500 mg/day) (N = 60) Group 3: a mixture of both fish oil capsules and vitamin B1 (N = 60) Group 4: placebo (N = 60) Participants took treatments as a single dose starting at the beginning of the menstrual cycle and continued for 2 consecutive months
Outcomes	Pain severity measured by VAS (scale 10 cm); pain duration (Cox Menstrual Scale). The study requested participants to complete a detailed questionnaire that assessed their menstrual pain and duration 3 times: at the study start, 1 month, and 2 months after taking the drugs or placebo
Notes	We presume that all participants had mild or severe pain, as all groups had a VAS score of 7.39 to 7.59 at baseline
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	“The girls were randomly assigned to 1 of 4 schedules.” Comment: the study authors did not describe the methods of sequence generation.
Allocation concealment (selection bias)	Unclear risk	Comment: the study authors did not describe the allocation concealment methods.
Blinding (performance bias and detection bias) All outcomes	Unclear risk	“A double‐blind, randomised, placebo‐controlled study carried on 240 high schools female students with dysmenorrhea in Urmia city by dividing into four groups with 60 members.” “They received drug boxes each month, and for all of them, possible drug complications were described and asked them to mention any occurred complications.” Comment: it is unclear whether or not the appearance of the treatment to both groups was the same in all aspects (different form; tablet, capsule).
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Comment: the study does not state how many participants were included in the analysis.
Selective reporting (reporting bias)	Unclear risk	Comment: the study authors did not prespecify adverse events as an outcome.
Other bias	Low risk	Comment: we did not identify any other potential sources of bias.