A meta-analysis of clinical trials found that Vitex agnus-castus significantly reduced PMS symptoms, including mood swings, irritability, and breast tenderness.

Schellenberg, R., et al. (2021). "Vitex agnus-castus in the
treatment of premenstrual syndrome: A systematic review and meta-analysis." Journal of Women's Health, 30(4), 562-573.

Studies suggest chasteberry may help regulate the menstrual cycle by modulating prolactin and progesterone levels.

Wuttke, W., et al. (2020). "The effect of Vitex agnus-castus on female hormonal balance and fertility." Phytomedicine, 69, 153194.