Our MR analysis of IGF‐I using a cis‐SNP is an example of the strongest case for an MR analysis, due to the strong plausibility of a biological link and a reduced likelihood of horizontal pleiotropy46, 47; therefore the association for this cis‐SNP indicates that IGF‐I may be driving the reported associations with prostate cancer risk. This evidence concerns the gene IGF1 and prostate cancer.