Power calculation for the general two-sample Mendelian randomization analysis

Mendelian randomization (MR) study has become a powerful approach to assess the potential causal effect of a risk exposure on an outcome. Most current MR studies are conducted under the two-sample setting by combining summary data from two separate genome-wide association studies (GWAS), with one providing measures on associations between genetic markers and the risk exposure, and the other on associations between genetic markers and the outcome. We develop a power calculation procedure for the general two-sample MR study, allowing for the use of multiple genetic markers, and shared participants between the two GWAS. This procedure requires a few easy-to-interpret parameters and is validated through extensive simulation studies.