A Case of Recurrence of Severe Depressive Disorder With Flu—Neuroinflammatory Basis of Depressive Disorder

This case highlights a relapse of major depressive disorder in an elderly man following a flu‐like illness, with clinical features and laboratory findings supporting a possible inflammatory contribution. It emphasises the relevance of the inflammatory theory of depression, especially in individuals with late‐life depression and recent immune activation. The patient's response to a tailored pharmacological and behavioural intervention further supports the potential role of inflammation in both the pathogenesis and treatment resistance of depressive episodes. This case contributes to the growing clinical recognition that systemic inflammation may not only coexist with but also influence the trajectory of mood disorders.