Abstract
Oral health is an integral component of overall well-being, with the oral cavity serving as a channel for external communication and expression of emotions such as stress and pessimism. Oral diseases can intensify feelings of depression, whereas depression can worsen oral health conditions. As a crucial part of the human microbiome, an imbalance in oral microbiota can release oral pathogenic microbes, which, through pathways including the circulation, nervous, and immune systems, can reach the brain and significantly affect the central nervous system. This can lead to dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis, further intensifying the development of depression. Similarly, an imbalance in oral microbiota in individuals with depression can intensify the occurrence of oral diseases. The relationship between depression and oral diseases is not isolated but rather a complex interplay in which they mutually influence and act as causative factors. To elucidate the causal relationship between oral diseases and depression and devise strategies for the prevention and treatment of both conditions, we explore the interaction mechanisms between oral diseases and depression from the perspective of oral microbiota. The occurrence of dental caries, periapical periodontitis, and periodontal diseases is closely associated with the excessive proliferation of specific bacteria in the oral cavity, such as Streptococcus mutans, Porphyromonas gingivalis, and Fusobacterium nucleatum. These bacteria can directly invade the brain through the compromised blood-brain barrier, activating pro-inflammatory cytokines and worsening depressive symptoms. Inflammatory conditions and ulcers in the oral mucosa are caused by various factors, including infection and immune abnormalities. Because of compromised immune function in individuals with depression, these inflammatory responses are often more severe and difficult to control. Malocclusion, trigeminal neuralgia, and temporomandibular joint disorders increase the risk of depression because of psychological stress and changes in the immune system. We also outline the diagnostic and therapeutic considerations for oral diseases in patients with depression, emphasizing the importance of early intervention for disease management. Future research will explore the therapeutic potential of oral microbiota in individuals with depression, with the aim to improve symptoms and treatment outcomes by adjusting oral microbiota, thus providing novel avenues for the prevention and treatment of depression.
