Black Cohosh - Clinical Studies

Clinical Studies on the Effectiveness of Black Cohosh

The following information on clinical studies of black cohosh was taken from information provided by the National Institute of Health, Office of Dietary Supplements.

Black cohosh is used primarily for treatment of hot flashes and other menopause symptoms. A number of studies using various designs have been conducted to determine whether black cohosh affects menopause symptoms1. Few studies were placebo controlled, and most assessed symptoms by using the Kupperman index-a scale that combines measures of hot flashes, insomnia, and depression but not vaginal dryness. Some of those with the best study designs are described below.

Excessive Sweating Decreased in Breast Cancer Survivors

A randomized, double-blind, placebo-controlled trial was done in breast cancer survivors because most of these women experience hot flashes and many use complementary or alternative remedies2. The women were over age 18 and had completed breast cancer treatment at least 2 months before the trial; 85 women (69 of whom completed the trial) took one tablet of placebo or 40 mg/day of black cohosh (as 20 mg twice daily) for 2 months to determine the effect on hot flashes, excessive sweating, palpitations, headaches, poor sleep, depression, and irritability [J.S. Jacobson, Columbia University, written communication, 2002]. Fifty-nine subjects were using tamoxifen (an antiestrogen treatment for breast cancer); tamoxifen users were distributed almost equally between the treatment and control groups. The frequency and intensity of hot flashes decreased in both groups, with no statistical difference between the groups; excessive sweating decreased significantly more in the treatment group than the placebo group. Other symptoms improved equally in both groups, and scores on a health and well-being scale did not change significantly in either group.

Symptoms Reduced in Women with Hysterectomy

A 24-week study in 60 women who had undergone hysterectomy but retained at least one ovary compared the effects of 8 mg/day of a black cohosh extract (as four 2-mg tablets daily; isopropanol extract version of Remifemin) with three estrogen regimens: estriol (1 mg/day), conjugated estrogens (1.25 mg/day), and estrogen-progestin therapy (one daily Trisequens® tablet containing 2 mg estradiol and 1 mg norethisterone acetate) 3. In all groups a modified Kupperman index measuring additional physical symptoms was significantly lower 4, 8, 12, and 24 weeks after treatment began. Black cohosh decreased symptoms similarly to the other treatments, but this study was not placebo controlled.

Daily Hot Flashes Decreased

A randomized, double-blind, placebo-controlled trial in 80 menopausal women compared 8 mg/day of a black cohosh extract (as two 2-mg tablets of Remifemin twice daily) with placebo or conjugated estrogens (0.625 mg/day) 4. At 12 weeks, scores on the Kupperman index and the Hamilton anxiety scale were significantly lower in the treated groups than in the placebo group; the scores of participants using black cohosh were somewhat better than the scores of those receiving the estrogen treatment. This is one of the few studies in which hot flashes were scored separately from other symptoms. Daily hot flashes decreased from 4.9 to 0.7 in the black cohosh group, 5.2 to 3.2 in the estrogen group, and 5.1 to 3.1 in the placebo group.

Symptoms Improved

A randomized, 12-week study of 55 menopausal women compared an ethanolic extract of black cohosh (40 drops twice daily) with conjugated estrogens (0.6 mg/day) or diazepam (2 mg/day) 5. Regardless of the treatment, all symptoms improved as measured by the Kupperman index, a depression scale, and an anxiety scale. However, this was not a blinded, placebo-controlled trial and diazepam is not a usual treatment for menopausal symptoms.

Further Study

Although these study results suggest that black cohosh may help relieve menopausal symptoms, studies of black cohosh have yielded conflicting data, in part because of lack of rigor in study design and short study duration (6 months or less). In addition, interpretation of these studies is complicated by the fact that different amounts of black cohosh from different sources were used in the various studies and their outcome measures were different. To provide more definitive evidence on the effects of black cohosh on menopausal symptoms, NCCAM (National Center for Complementary and Alternative Medicine) is funding a 12-month, randomized, placebo-controlled study to determine whether treatment with black cohosh is effective in reducing the frequency and intensity of menopausal hot flashes. The study will also assess whether black cohosh reduces the frequency of other menopausal symptoms and improves quality of life. The study will examine the possible mechanisms of action of black cohosh.

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References:

1. Jacobson JS, Troxel AB, Evans J, et al.: Randomized trial of black cohosh for the treatment of hot flashes among women with a history of breast cancer. Journal of Clinical Oncology 19: 2739-2745, 2001.
2. Lehmann-Willenbrock E, Riedel H-H: Clinical and endocrinological studies on the therapy of ovarian defunctionalization symptoms after hysterectomy sparing the adnexa (in German). Zentralblatt fur Gynakologie 110: 611-618, 1988.
3. Stoll W: Phytotherapy influences atrophic vaginal epithelium: Double-blind study of Cimicifuga vs. estrogenic substances (in German). Therapeutikon 1: 23-31, 1987.
4. Warnecke, G: Influencing of menopausal complaints with a phytodrug: successful therapy with Cimicifuga monoextract (in German). Medizinische Welt 36: 871-874, 1985.
5. American College of Obstetricians and Gynecologists: Use of botanicals for management of menopausal symptoms. ACOG Practice Bulletin 28: 1-11, 2001.