Pan Y, et al. - Researchers conducted this Mendelian randomization study to investigate the causal relationships of Lp(a) concentrations on ischemic stroke, ischemic stroke subtypes, and Alzheimer disease. For this investigation, 9 single-nucleotide polymorphisms related to Lp(a) concentrations as instrumental variables were used. The authors obtained summary-level data on ischemic stroke and its subtypes from the Multiancestry Genome-Wide Association Study of Stroke consortium with ≤ 446,696 people in Europe. According to findings, a causal association was found between high Lp(a) concentrations and an increased risk of large artery stroke but a reduced risk of small vessel stroke and Alzheimer disease. Further investigation is required of the mechanism underlying the double-edged sword effect of Lp(a) concentrations on the neurological system. No evidence of pleiotropic bias was identified by MR-Egger.