Vitex agnus-castus, also known as chaste tree berry, is used to support and treat premenstrual syndrome (PMS) primarily based on scientific evidence, though it has a long history of traditional use as well. Multiple randomized controlled trials and systematic reviews have reported that Vitex agnus-castus extract can significantly reduce PMS symptoms, including breast tenderness, irritability, mood swings, and headaches. The proposed mechanism involves modulation of prolactin levels via dopaminergic effects, which may help correct hormonal imbalances that contribute to PMS symptoms.

A 2012 Cochrane review concluded that Vitex agnus-castus is more effective than placebo for global symptom relief of PMS, although the authors noted that more high-quality studies are needed. The European Medicines Agency (EMA) also recognizes its traditional and well-established use for relieving minor symptoms of PMS. Dosages used in clinical studies typically range from 20-40 mg of extract daily.

Overall, while more large-scale, high-quality clinical trials would further strengthen the evidence, current data provide moderate to strong scientific support for the use of Vitex agnus-castus in managing PMS symptoms.