A recent study by Richmond et al. [30] combined several of these methods to investigate causality between BMI and methylation at HIF3A (a gene linked to metabolism and obesity, and associated with adiposity in multiple EWAS [31, 32]), including bidirectional Mendelian randomisation analysis, longitudinal analysis of HIF3A methylation, and analysis of association between maternal pregnancy BMI and HIF3A methylation in offspring at birth (using cord blood). Here, HIF3A is linked to obesity disorder.