Biological Pathways Linking Cancer and Major Depressive Disorders

Abstract

Cancer is widely recognized as a physical disease, but it can also have significant effects on mental health. Approximately 15-25% of cancer patients experience major depressive disorder (MDD) or clinically significant depressive symptoms. Growing evidence indicates that chronic inflammation and immune activation may contribute to cancer-related depression, although the biological mechanisms underlying this relationship are not yet fully understood. This review examines the inflammatory pathways linking cancer and depression, with a particular focus on how chronic inflammation, immune activation, inflammatory biomarkers impact brain function. Current evidence suggests that inflammatory cytokines, including interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-α), and C-reactive protein (CRP), may influence neurotransmitter signaling and contribute to depressive symptoms. However, most available evidence remains observational, making it difficult to establish a direct relationship between inflammation and depression. Overall, this review highlights chronic inflammation as a key biological mechanism that may contribute to depression in cancer patients while emphasizing the need for further research to clarify the relationship between inflammation and depressive symptoms. A better understanding of these mechanisms may improve the recognition and management of depression while guiding future research and more personalized approaches to cancer care.