IL6 and major depressive disorder: Table 5 summarizes studies of the relationship between DNA methylation of cytokine genes and antidepressant medication use. Ryan et al. 2017 compared methylation of the IL6 gene in buccal cells from 92 >65-year-old subjects with and without MDD/high depressive symptoms and 288 HC [82]. Depression was associated with decreased IL6 methylation compared to controls, while antidepressant use was associated with an increase. Over half of MDD subjects took antidepressants in the SSRI class [82]. Another study conversely observed decreased IL-6 levels after antidepressant treatment [83].