In the MDD group, we did not find any significant difference between plasma S100B levels and age (r = –0.09, p = 0.208), education (r = 0.01, p = 0.875), BMI (r = 0.02, p = 0.748), duration (r = 0.04, p = 0.630), first-onset (r = 0.102, p = 0.167), medication-naïve (r = –0.069, p = 0.350), suicidal ideation (r = 0.09, p = 0.225), suicidal behaviour (r = 0.12, p = 0.114), HAMD-17 scores (r = 0.06, p = 0.394), or HAMA scores (r = 0.06, p = 0.458). Here, S100B is linked to major depressive disorder.