CST9 and major depressive disorder: Contrasting BPD with MDD subjects, most significant results of multivariate analyses resulted in significantly different methylated CpG sites located e.g., within the gene coding for a ligand of Eph-related receptor tyrosine kinases (EFBN1), closely to the gene coding for a suppressor of cytokine signaling (SOCS) family member (SPSB2) and near the gene coding for a protein similar to mouse cystatin 9 (CST9L).