Significant inverse correlations were observed between SLC6A4 DNA methylation and FA (CpG3, Pearson's correlation: r=−0.493, P=0.003) and axial diffusivity (CpG3, Pearson's correlation: r=−0.478, P=0.004) values of the body of the corpus callosum in patients with MDD. This evidence concerns the gene SLC6A4 and major depressive disorder.