Yang H, et al. - In order to clarify a causal link between age at menarche (AAM) and risk of epithelial ovarian cancer (EOC), researchers conducted two-sample Mendelian randomization (MR) analyses following systematic meta-analyses. To quantitatively assess the link between AAM and risk of ovarian cancer, they carried out meta-analyses with 11,410 cases and 1,163,117 noncases. For Chinese and for Europeans, 25 single nucleotide polymorphisms (SNPs) and 390 SNPs, respectively, associated with AAM were used as instrumental variables in MR analyses. According to meta-analyses, case-control studies reported an inverse link between per year older AAM and risk of ovarian cancer, but cohort studies showed no such link. Overall, a causal link between AAM and EOC risk was shown in this study.