Abstract: Sixteen randomised controlled trials, recruiting a total of 2027 perimenopausal or postmenopausal women, were identified. All studies used oral monopreparations of black cohosh at a median daily dose of 40 mg, for a mean duration of 23 weeks. Comparator interventions included placebo, hormone therapy, red clover and fluoxetine. Reported outcomes included vasomotor symptoms, vulvovaginal symptoms, menopausal symptom scores and adverse effects. There was no significant difference between black cohosh and placebo in the frequency of hot flushes (mean difference (MD) 0.07 flushes per day; 95% confidence interval (CI) -0.43 to 0.56 flushes per day; P=0.79; 393 women; three trials; moderate heterogeneity: I2 = 47%) or in menopausal symptom scores (standardised mean difference (SMD) -0.10; 95% CI -0.32 to 0.11; P = 0.34; 357 women; four trials; low heterogeneity: I2 = 21%). Compared to black cohosh, hormone therapy significantly reduced daily hot flush frequency (three trials; data not pooled) and menopausal symptom scores (SMD 0.32; 95% CI 0.13 to 0.51; P=0.0009; 468 women; five trials; substantial heterogeneity: I2 = 69%). These findings should be interpreted with caution given the heterogeneity between studies. Comparisons of the effectiveness of black cohosh and other interventions were either inconclusive (because of considerable heterogeneity or an insufficient number of studies) or not statistically significant. Similarly, evidence on the safety of black cohosh was inconclusive, owing to poor reporting. There were insufficient data to pool results for health-related quality of life, sexuality, bone health, vulvovaginal atrophic symptoms and night sweats. No trials reported cost-effectiveness data. The quality of included trials was generally unclear, owing to inadequate reporting. There is currently insufficient evidence to support the use of black cohosh for menopausal symptoms. However, there is adequate justification for conducting further studies in this area. The uncertain quality of identified trials highlights the need for improved reporting of study methods, particularly with regards to allocation concealment and the handling of incomplete outcome data. The effect of black cohosh on other important outcomes, such as health-related quality of life, sexuality, bone health, night sweats and cost-effectiveness also warrants further investigation.

Plain-language summary: The herb black cohosh was traditionally used by Native Americans to treat menstrual irregularity, with many experimental studies indicating a possible use for black cohosh in menopause. This review set out to evaluate the effectiveness of black cohosh for controlling the symptoms of menopause. The review of 16 studies (involving 2027 women) found insufficient evidence to support the use of black cohosh for menopausal symptoms. Given the uncertain quality of most studies included in the review, further research investigating the effectiveness of black cohosh for menopausal symptoms is warranted. Such trials need to give greater consideration to the use of other important outcomes (such as quality of life, bone health, night sweats and cost-effectiveness), stringent study design and the quality reporting of study methods.