If that is the case, all the other factors that can potentially bias an observation are distributed equally. ...any differences in the endpoints in the population of interest are deemed to be due to the allele of interest. ...the effect of the alleles of interest is seen after a lifelong exposure in a Mendelian randomized study, whereas the results of the drug effects depend upon the study duration. ...the effect size predicted by a Mendelian randomized study may be considerably higher than that seen in a clinical trial. ...while Mendelian randomized studies are useful for hypothesis generation, drugs in clinical trials frequently have “off-target” effects that cannot be predicted based on a Mendelian randomization study.