Five-leaf Chastetree, more commonly referred to as Vitex agnus-castus or chasteberry, is widely used for the management of premenstrual syndrome (PMS), particularly PMS Type A, which is characterized by symptoms such as mood swings, irritability, anxiety, and tension. The use of Vitex for PMS has roots in traditional European herbal medicine, but its efficacy has also been supported by modern scientific research. Several randomized, double-blind, placebo-controlled trials have demonstrated that extracts of Vitex agnus-castus can significantly reduce the severity of PMS symptoms, especially those related to mood and affect, which are predominant in PMS Type A.

The proposed mechanism involves modulation of the hypothalamic-pituitary axis, particularly by binding to dopamine receptors, which leads to a reduction in prolactin secretion. Elevated prolactin levels are associated with PMS symptoms, and their reduction is thought to help restore hormonal balance, thereby alleviating symptoms. Systematic reviews and meta-analyses (e.g., by the Cochrane Collaboration) have found moderate to strong evidence for the effectiveness of Vitex extracts in treating PMS, with relatively few adverse effects reported in clinical trials.

While further large-scale studies are warranted, the current scientific literature supports the use of Five-leaf Chastetree as a reasonably effective and well-tolerated treatment option for PMS Type A symptoms.