Chaste tree (Vitex agnus-castus) is commonly used to support PMS, specifically PMS Type P (premenstrual syndrome characterized by premenstrual pain, primarily breast tenderness, and irritability, often associated with high estrogen and low progesterone). There is a solid base of scientific evidence supporting its effectiveness for these symptoms. Multiple randomized, placebo-controlled clinical trials have demonstrated that chaste tree extract significantly reduces symptoms of PMS, including breast pain (mastalgia), mood swings, and irritability. The mechanism appears to involve modulation of the pituitary gland, resulting in increased luteinizing hormone (LH) release and consequently enhanced progesterone production during the luteal phase, helping to correct the estrogen-progesterone imbalance typical of PMS Type P.

For example, a 2001 randomized controlled trial published in the British Medical Journal found that women taking Vitex agnus-castus extract experienced a significant reduction in PMS symptoms compared to placebo, with breast tenderness and irritability among the most improved. Meta-analyses and systematic reviews have confirmed these findings, generally rating the evidence as moderate to strong. While some studies note mild side effects (e.g., gastrointestinal upset), chaste tree is considered safe for most women.

In summary, chaste tree's use for PMS Type P is scientifically validated, with an evidence rating of 4 out of 5, reflecting multiple well-controlled studies and meta-analyses supporting its efficacy in addressing premenstrual symptoms, especially those linked to hormonal imbalances.