Inflammatory Cytokines as a Shared Pathophysiological Pathway in Depression and Chronic Insomnia: A Narrative Review of Mechanisms and Clinical Implications

The comorbidity of depression and chronic insomnia is very common in clinical practice, and there is a complex and close relationship between these two diseases, yet its underlying mechanisms remain incompletely understood. In recent years, inflammatory cytokines have been widely studied as important etiological factors for depression comorbid with chronic insomnia. However, whether inflammation is a cause or consequence of this comorbidity remains debated.This review synthesizes emerging evidence to position inflammatory cytokines not merely as correlates, but as central drivers in the pathophysiological nexus of depression and chronic insomnia. It systematically expounds the inflammatory characteristics and clinical significance of patients with depression comorbid with chronic insomnia, with the aim of reviewing the evidence of the association between inflammatory cytokines and depression comorbid with chronic insomnia, and discussing the potential pathophysiological mechanisms that may explain this association, thereby providing a robust scientific foundation for the development of novel ant-inflammatory therapeutic strategies and precision medicine approaches for this challenging comorbidity.