Kashanian 2013.

Methods	RCT
Participants	Included: single women from 18 to 25 years of age, whose dysmenorrhoea started at menarche, without any increase over time, regular menstrual cycles, and normal pelvic examination Excluded: women that had any pelvic and abdominal surgeries, prior genital infection or pelvic pain, used other sedatives during the cycle, history of psychological problems or drug use, abnormal or heavy bleeding, smoking or alcohol consumption, digestive problems, prolonged stress in family or job, known pelvic or uterine anomaly, abnormal ultrasound of uterus and ovaries, and vitamin E allergy Age: vitamin E group = 22.8 years, placebo = 23.5 years Source: randomised 120 women aged 18 to 25 with primary dysmenorrhoea, of whom only 94 finished the study and were analysed. One woman had mild pain (VAS < 3), 44 had moderate pain (VAS 3 to 7) and 49 had severe pain (VAS 7 to 10) Location: Iran
Interventions	Group 1: vitamin E 400 IU/day for 2 days before and 3 days after menses (total 5 days), for 2 cycles (N = 60, 42 analysed) Group 2: placebo (N = 60, 52 analysed)
Outcomes	Pain severity (VAS scale 10 cm) at 2 months.
Notes	One woman had only mild dysmenorrhoea (and it is unclear which group she was in)
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Comment: participants chose an envelope.
Allocation concealment (selection bias)	Unclear risk	Comment: the study used sealed sequentially distributed envelopes labelled A, B, C, or D.
Blinding (performance bias and detection bias) All outcomes	Unclear risk	Comment: outcome assessors and treating physicians were blinded. Vitamin E and placebo were identical in shape, colour, taste, and smell.
Incomplete outcome data (attrition bias) All outcomes	High risk	Comment: only 42/60 participants in the intervention group and 52/60 of the control group completed the study. The dropout rate was 21.7% (26/120).
Selective reporting (reporting bias)	Unclear risk	Comment: adverse effects were not reported.
Other bias	Low risk	Comment: we did not identify any other potential sources of bias.