The efficacy of Hypericum perforatum (St John's wort) for the treatment of premenstrual syndrome: a randomized, double-blind, placebo-controlled trial

Canning S, et al.

Published in CNS Drugs

Methodology

Randomised, double-blind, placebo-controlled crossover trial; two menstrual cycles of St John's wort 900 mg/day versus placebo with washout, using the Daily Symptom Report and standardised PMS rating scales.

Key Findings

In 36 women with premenstrual syndrome, Hypericum perforatum 900 mg/day (standardised to 0.18% hypericin) over two menstrual cycles reduced physical and behavioural PMS symptoms significantly more than placebo (roughly 50% greater symptom reduction), while mood and pain subscales did not differ significantly.

Conclusions

No significant effects of Hypericum perforatum compared with placebo for mood- and pain-related PMS symptoms.

Limitations

Small sample of 36 women reduces precision; crossover design with potential carryover across cycles; symptom diaries self-reported; short exposure of two cycles per condition; single extract and dose tested.