SLC6A4 and major depressive disorder: In a study conducted by Stonawski et al. [19] (167 children aged 6-9 years), the diagnosis of depression during pregnancy was associated with reduced methylation in the gene encoding the glucocorticoid receptor (NR3C1), the gene encoding the mineralocorticoid receptor (NR3C2), and in the gene for the serotonin receptor (SLC6A4).