increased the AUC of the discovery sample until the value was maximized. This set of loci was then used to predict PPD status in the replication sample. The algorithm returned two loci at CpGs cg21326881 and cg00058938, corresponding to the promoter regions of the HP1BP3 and TTC9B genes, respectively, which resulted in an AUC of 0.92 in the discovery sample and 0.9 in the replication sample (Supplementary Figure 3b). A genome-wide significance for this biomarker set of P=0.041 was determined by Monte Carlo permutation analysis.
