Five-leaf Chastetree (Vitex negundo) is closely related to Vitex agnus-castus (Chasteberry), which has been more extensively studied for its effects on premenstrual syndrome (PMS), particularly PMS Type P (premenstrual pain and physical symptoms). While direct studies on Vitex negundo are limited, there is moderate to strong scientific evidence supporting the use of the Vitex genus, especially V. agnus-castus, for alleviating PMS symptoms.

Clinical trials and meta-analyses have shown that extracts of Vitex agnus-castus can significantly reduce symptoms such as breast pain, bloating, and irritability. The presumed mechanism is modulation of prolactin secretion via dopaminergic activity, which may help balance hormonal fluctuations associated with PMS. Vitex negundo, although less studied, shares similar phytochemical constituents, such as flavonoids and iridoids, and has traditional use in Ayurvedic and Southeast Asian medicine for gynecological complaints, including menstrual pain and irregularities.

Given the phylogenetic and phytochemical similarities, and supporting traditional use, the use of Five-leaf Chastetree for PMS Type P is considered scientifically plausible, though direct clinical evidence is somewhat limited compared to V. agnus-castus. The overall rating reflects strong evidence for the genus and plausible benefit for V. negundo, but more targeted research on Five-leaf Chastetree itself would further clarify its efficacy.