In this "Evidence-based review of therapies at the menopause, . . . the highest level of scientific evidence available for each therapy for menopausal symptoms was sought, for example, systematic reviews of randomised controlled trials (RCTs)."
and the conclusion reached was that
"No complementary medicine, for example, phytoestrogens, black cohosh, herbal or homeopathic medicines or complementary therapies, for example, acupuncture, yoga, chiropractic manipulation, reflexology or magnetic devices have a greater effect than the usual placebo effect seen in quality blinded RCTs."
onlinelibrary.wiley.com/doi/10.1111/j.1744-1609.2009.00133.x/abstract
It seems that it works by suggestion, like many placebos.