Ref (type)	Population	Outcome, Interventions	Results and statistical analysis	Effect size	Favours
Absence from work or school
Systematic review	24 women with primary dysmenorrhoea Data from 1 RCT	Mean number of lost hours each menstrual cycle 1.46 hours with high-frequency TENS 1.42 hours with placebo TENS	WMD +0.04 hours 95% CI –0.4 hours to +0.5 hours Randomisation and blinding unclear		Not significant