Figure 1.

A 2-step epigenetic Mendelian randomization approach to the study of relationships between cigarette smoking, methylation, and inflammation. Rectangular dark boxes represent variables of interest at each step, and light boxes represent variables of interest at the other step. Solid dark arrows indicate the directed association of interest at each step, and dashed gray arrows indicate the directed association of interest at the other step. Single nucleotide polymorphism (SNP) S is an instrument SNP or a genetic risk score for smoking, and SNP C is an instrument SNP or a genetic risk score for methylation levels.