BDNF and depressive disorder: After adjustment for age, sex and antidepressant use, methylation of CpG unit 3.4.5 in BDNF promoter I (β=0.094, s.e.=0.029 and P=0.001) and CpG 3 in promoter IV (β=0.31, s.e.=0.14 and P=0.025) remained significantly associated with depression (Supplementary Table S5).