Vitex agnus-castus, commonly known as Vitex or chaste tree, is often used in herbal medicine to support symptoms associated with PMS Type S (premenstrual syndrome with significant swelling, bloating, and breast tenderness, typically attributed to excess estrogen or prolactin). Scientific evidence supports its use primarily due to its dopaminergic effects, which reduce prolactin secretion via action on dopamine receptors in the pituitary gland. Elevated prolactin is associated with cyclical mastalgia (breast pain) and water retention, both hallmarks of PMS Type S.

Multiple randomized controlled trials and meta-analyses have found that Vitex extract can significantly reduce symptoms such as breast tenderness, edema, and mood disturbances in women with PMS. The evidence base is moderate, with several high-quality studies but also some with methodological limitations. For example, a 2012 Cochrane review concluded that Vitex is more effective than placebo for overall PMS symptoms, particularly mastalgia, though more robust studies are needed. Traditional use also supports Vitex for menstrual complaints, but scientific validation (especially for PMS with predominant swelling and breast discomfort) gives it a rating of 3 out of 5 for evidence.

In summary, Vitex is scientifically supported for use in PMS Type S due to its prolactin-lowering effects, but while the evidence is promising, it is not yet conclusive or universally accepted, warranting a moderate evidence rating.