PTPN22 and major depressive disorder: For example, among the candidate genes were known susceptibility loci for diabetes (PTPN22, CEP68, RREB1, TCF7L2 [31]), coronary artery disease (PSRC1, UNC5C, LPLA [32]), depression (MAD1L1, YLPM1 [33,34]) and insomnia (NMT1 [35]).