IL6 and major depressive disorder: Oxidative stress, including reactive oxygen and nitrogen species (ROS/RNS), accumulates in the body as one ages and impairs muscle, causing the decline of HGS.26 ROS/RNS have also been related to MDD.27 Inflammatory factors, such as C reactive protein and interleukin-6, can both accelerate the catabolism of muscle28 and induce depressive symptoms.29 These biochemical processes affect movement and quality of life, indirectly causing low mood and even depressive symptoms.