Evidence Level
Strong
Vitex agnus-castus has one of the strongest clinical evidence bases among herbal remedies for women's health. The landmark Schellenberg (2001) RCT demonstrated significant PMS symptom reduction with Ze 440 extract in 170 women, with a 52% improvement rate vs 24% for placebo. A systematic review by Verkaik et al. (2017) analyzed 12 RCTs and 2 systematic reviews, concluding that vitex is effective for total PMS symptoms, particularly psychological complaints, with a favorable safety profile. The mechanism is well-characterized: vitex diterpenes act as dopamine D2 receptor agonists in the anterior pituitary, reducing prolactin secretion and allowing normal corpus luteum function and progesterone production.