Randomised controlled trials (RCTs) of preparations that contained black cohosh compared with placebo in perimenopausal or postmenopausal women were eligible for inclusion. Trials were required to report the primary outcome of frequency of vasomotor symptoms. Studies conducted exclusively in women with a history of breast cancer were excluded.
More than half of the included studies administered black cohosh (20mg to 160mg) in combination with other products that included St John's wort, dong quai root, milk thistle extract, red clover flower extract, ginseng, chaste-tree berry fruit extract, isoflavones, lignans, soy extract, primrose oil, vitamin D, vitamin E and calcium.
Included studies used different scales to quantify the frequency of vasomotor symptoms. These included Kupperman index, Menopausal Rating Scale, Menopausal Rating Score I, Menstrual Rating Score and number of hot flushes.
The average age of women ranged from 50.5 to 59 years. All included studies excluded patients with a history of hormone-dependent cancer and/or previous use of hormones unless followed by a washout period.
Two reviewers independently selected studies for inclusion.