According to a previous study, psychological factors such as stress and depression cause physiological changes to physical functions such as the nervous system, endocrine system, and immune system; increase the incidence of infections by raising the levels of C-reactive protein, interleukin (IL)-1, and IL-6; and increase the incidence of periodontal diseases and tooth loss by destroying periodontal tissues [18]. Here, IL6 is linked to major depressive disorder.