2.6. Plasma Measurements
peripheral venous blood
After saliva collection, 4 mL of fasting peripheral venous blood was taken from participants. Anticoagulant was added into the blood collection tube, and plasma was separated by 3000 r/min and stored in a low temperature freezer (−80 °C). The Cortisol CLIA Microparticles (Autobio Diagnostics Co., Ltd., Zhengzhou, China) and the ACTH CLIA Microparticles (Autobio Diagnostics Co., Ltd.) were used to detect the levels of cortisol and adrenocorticotropin (ACTH) in plasma.