Vitex agnus-castus, commonly known as chaste tree or chasteberry, is widely used for the management of premenstrual syndrome (PMS), particularly PMS Type A (characterized by anxiety, irritability, and mood swings). The justification for its use is grounded in both traditional herbal medicine and a growing body of scientific literature, with several randomized controlled trials and meta-analyses supporting its efficacy.

The primary proposed mechanism is Vitex's dopaminergic action, which leads to the suppression of prolactin release from the pituitary gland. Elevated prolactin levels have been associated with PMS symptoms, especially those related to mood and affect. Vitex is thought to indirectly balance estrogen and progesterone levels, thus ameliorating the cyclical symptoms experienced in PMS Type A.

Multiple clinical studies have demonstrated that Vitex extract can reduce the severity of PMS symptoms, particularly those related to mood disturbances. A 2012 Cochrane review concluded that Vitex may be more effective than placebo in reducing overall PMS symptoms, though the quality of evidence was moderate and more large-scale studies are needed. Safety profiles in clinical use are generally favorable with minimal adverse effects.

In summary, while there is a long tradition of using Vitex for PMS, current scientific evidence provides moderate support for its efficacy, especially for mood-related symptoms seen in PMS Type A.