MendelR: A One‐Stop R Toolkit for Mendelian Randomization Analysis

ABSTRACT MendelR is a fully automated R package specifically developed for Mendelian randomization (MR) studies, designed to address the technical challenges of causal inference in biomedical research. As a powerful causal inference method, Mendelian randomization can effectively reduce confounding bias in observational studies. However, its complex data processing workflow, diverse analytical approaches, and stringent hypothesis‐testing requirements often deter researchers. MendelR integrates the latest eQTL and pQTL databases, along with multi‐omics resources, to provide a one‐stop solution covering data acquisition, preprocessing, and instrumental variable selection, through to various MR analysis methods, thereby significantly lowering the technical barriers to research. This toolkit supports not only standard two‐sample MR analysis but also encompasses advanced applications, including mediation analysis, multivariate MR, drug target analysis, and multi‐omics integration. It also incorporates rigorous sensitivity analyses and multiple‐testing correction mechanisms to ensure the reliability of research findings. With its user‐friendly interface, fully automated workflow, and diverse visualization features, MendelR offers an efficient and accurate MR analysis platform for researchers at all levels, from beginners to seasoned professionals, thereby advancing the in‐depth development of causal relationship research in the biomedical field.