S100A8 and psychosocial stress measurement: Psychological stress induced a significant elevation in plasma S100A8/A9 measured at 20 min after test completion compared to baseline [median (IQR) 750 (615–1190) ng/mL pre-stress vs 910 (720–1452) ng/mL post-stress; p = 1.8 × 10−8] (Fig. 1).