S100B and major depressive disorder: This biomarker has gained much attention as a recent meta-analysis found that S100B was increased in schizophrenia spectrum disorders (24 studies; 1107 patients; standardized mean difference (SMD) = 0.82; 95% confidence interval (CI) = 0.51 to 1.13; I2 = 90%), major depression (13 studies; 584 patients; SMD  = 0.57; 95% CI = 0.31 to 0.83; I2 = 73%) and bipolar disorder (4 studies; 142 patients; SMD  = 0.55; 95% CI = 0.16 to 0.94; I2 = 48%) (Futtrup et al. 2020).