Chastetree (Vitex agnus-castus), also known as chasteberry, has been traditionally used for various gynecological conditions, including menstrual irregularities and premenstrual syndrome (PMS). Its use for PMS Type A—characterized primarily by symptoms of anxiety, irritability, and mood swings—has received scientific attention. The primary mechanism is believed to be modulation of dopaminergic activity in the pituitary gland, leading to decreased prolactin secretion. Elevated prolactin is associated with many PMS symptoms, particularly mood-related ones.

Multiple randomized, placebo-controlled clinical trials have demonstrated that Vitex agnus-castus extract can significantly reduce PMS symptoms, especially those of the emotional and psychological variety. A 2001 study published in the British Medical Journal involving over 170 women found a significant improvement in PMS symptoms, with the greatest benefit in irritability, mood alteration, anger, and headache. Additional meta-analyses and systematic reviews, including a 2017 Cochrane review, concluded that chasteberry is more effective than placebo for global symptom improvement in PMS, though more large, high-quality studies are encouraged.

Its safety profile is generally favorable, with mild side effects such as gastrointestinal disturbances occasionally reported. In summary, the use of Chastetree for PMS Type A is supported by scientific research, particularly for mood-related symptoms.