KITLG and bipolar disorder: KITLG methylation level was significantly lower in bipolar disorder patients compared to the healthy controls (mean control = 0.185, mean bipolar = 0.139) (β = −0.351, t = −6.316 p < 0.001; model fit: F = 18.56, p < 0.001, R2 = 0.407) after adjustment for age, gender, childhood adversity, smoking, and cell types.