A 2017 systematic review observed eight clinical trials for the effects of preparations of V. agnus castus on the diagnostic criteria of PMS and PMDD. The results all showed positive outcomes in the reduction of symptoms using various assessment tools.
References:
Cerqueira RO, Frey BN, Leclerc E, Brietzke E. Vitex agnus castus for premenstrual syndrome and premenstrual dysphoric disorder: a systematic review. Arch Womens Ment Health. 2017;20(6):713–719. doi:10.1007/s00737-017-0791-0 https://pubmed.ncbi.nlm.nih.gov/29063202/