Chaste tree (Vitex agnus-castus) is widely used to support symptoms of premenstrual syndrome (PMS), including PMS Type H, which is characterized by symptoms such as water retention, breast tenderness, and bloating—often attributed to high estrogen ("H" for "hyperestrogenism" or "hyperhydration"). The use of chaste tree for PMS is supported by both historical tradition and an increasing body of scientific evidence.

Several randomized, double-blind, placebo-controlled studies have demonstrated the efficacy of chaste tree extract in reducing PMS symptoms. Clinical trials have reported significant improvements in breast tenderness, edema, and mood symptoms compared to placebo. The proposed mechanism involves modulation of the hypothalamic-pituitary axis, leading to decreased prolactin secretion and potential rebalancing of estrogen and progesterone. This is particularly relevant to PMS Type H, where elevated prolactin and relative estrogen excess can exacerbate symptoms.

A 2017 meta-analysis in Phytomedicine and a Cochrane review concluded that chaste tree is more effective than placebo in relieving overall PMS symptoms, with a favorable safety profile. While not all studies separated PMS subtypes, improvements in mastalgia (breast pain) and fluid retention are commonly reported. Thus, there is scientific validation—though not absolute consensus—for the use of chaste tree in PMS Type H, with a moderate-to-strong evidence base.