Fig. 1

Study design overview. Abbreviations: NAFLD, non-alcoholic fatty liver disease; SNP, single nucleotide polymorphisms. There are three assumptions of mendelian randomization design. The first assumption is that the genetic variants used as instrumental variables should be robustly associated with the exposure; the second assumption is that the used genetic variants should not be associated with any confounders; and the third assumption is that the selected genetic variants should affect the risk of the outcome merely through the risk factor, not via alternative pathways.