In this 2018 comparative randomized, double-blind clinical study, researchers reviewed the efficacy of Cimicifuga racemosa in comparison with evening primrose oil (EPO). 80 postmenopausal women with menopause-related symptoms were assessed. Authors concluded both herbs were effective in reducing the severity of hot flashes and improvement of the quality of life, though black cohosh more significantly reduced the number of hot flashes experienced over eight weeks.
Mehrpooya, M., Rabiee, S., Larki-Harchegani, A., Fallahian, A. M., Moradi, A., Ataei, S., & Javad, M. T. (2018). A comparative study on the effect of “black cohosh” and “evening primrose oil” on menopausal hot flashes. Journal of education and health promotion, 7, 36. https://doi.org/10.4103/jehp.jehp_81_17