Mendelian Randomisation (MR) From a naturally randomised process to a trendy research design

Abstract

Mendelian Randomisation (MR) is an application of Mendel’s second law in which genotype of one trait from parents is passed on to their offspring randomly and independent on other traits (i.e., the law of independent assortment). This principle, ideally, makes MR less prone to the confounder and reverse causality, compared with a traditional observational design. In MR, single nucleotide polymorphisms (SNPs) are used as a proxy of exposure, then their association with an outcome of interest is examined. Due to the advancement of human genomic area, SNPs-chip used for the detection of SNPs becomes relatively cheap and more efficiency, and this leads to the increase in the popularity of MR study design over the last decade. In this article, the background and the key principle of MR in comparison with randomised controlled trials (RCTs) are described. Moreover, the current methodology used in MR along with the main caveats of MR design is illustrated. The aim of this article is to help health care professionals gain more confidence and basic understanding when they come across the articles about MR.