VDR and major depressive disorder: Zhang F et al. reported the genetically determined PTSD confers a causal effect on depression and depressed affect, but not major depressive disorder [50], moreover, deep learning or machine learning is a hot topic in classification and prediction of diseases based on biomarkers [51, 52], which inspired us to conduct the causal inference analysis of the functional VDR polymorphisms in CAD and discuss the possibility to use the vitamin D receptor genetic variants related to CHD for the prediction or early diagnosis of CHD in our next mechanism study.