Chastetree (Vitex agnus-castus), also known as chasteberry, is commonly used for premenstrual syndrome (PMS), including PMS Type H (characterized by symptoms such as breast swelling/tenderness and fluid retention, often associated with elevated estrogen levels). The scientific rationale for using Chastetree in PMS Type H centers on its dopaminergic effects, which can reduce prolactin secretion from the pituitary gland. Elevated prolactin is implicated in cyclical mastalgia (breast pain), a core symptom of PMS Type H.

Several randomized, placebo-controlled clinical trials have evaluated Chastetree extract for PMS symptoms, including breast tenderness, bloating, irritability, and mood swings. Notably, a 2001 multicenter, double-blind trial published in the BMJ (n=170) found significant improvements in symptoms, including breast tenderness, with Chastetree compared to placebo. A 2012 Cochrane review concluded that Vitex agnus-castus may be more effective than placebo in treating global PMS symptoms, though highlighted methodological limitations in many studies.

While the evidence is strongest for breast-related symptoms (relevant to PMS Type H), most studies assess overall PMS rather than subtypes. The overall evidence base is moderate; some studies are small or have risk of bias, but the physiological rationale is supported by preclinical and clinical data. Therefore, Chastetree is considered to have moderate scientific support for alleviating PMS Type H symptoms, particularly mastalgia and fluid retention.