DISC1 and major depressive disorder: SNP rs16856189 has an r2 of 0.27 with rs16856199, which may explain in part why this association has not been reported previously in genome-wide association studies.22, 62, 63 SNP rs6678723, which lies 2.1 kb distal to this SNP within intron 11, showed the most significant association of DISC1 in the recent mega-analysis of depression (P=0.0092).20