IFNG and rheumatoid arthritis: These results may explain the portion of etiology for “morning stiffness of joints,” a common complaint and one of the best indicators of the condition of RA patients, correlates with the secretion of TNF-α, IL-6, and IFN-γ, whose levels peak from midnight to early in the morning [36], and chronobiology-based approach has been tested and shown to improve the morning symptoms of RA [37, 38].