Abstract
Depressive disorder is a highly prevalent psychiatric condition that imposes substantial psychological burden on patients and their families, as well as significant economic costs to society. A close relationship exists between depressive disorders and abnormalities in olfactory function, and depressive disorders are frequently accompanied by marked impairments in social functioning. Patients exhibit dysfunction across multiple dimensions of olfactory processing, including olfactory sensitivity, identification, discrimination, and memory, and these abnormalities are influenced by symptom severity and stage of illness. Individuals with depressive disorder show reduced olfactory bulb volume, structural and functional abnormalities in the olfactory cortex, and altered structural and functional connectivity in emotion-related brain regions, such as the amygdala. These neural alterations are associated not only with olfactory dysfunction but also closely with depressive symptoms, providing a neurobiological basis for understanding the emotional and social deficits accompanying depressive disorders. Olfactory dysfunction associated with depressive disorders is characterized by reduced olfactory sensitivity and impaired odor identification, often accompanied by social withdrawal and other forms of diminished social functioning. Reduced olfactory bulb volume, abnormalities in the structure and functional connectivity of emotion-related regions such as the amygdala, along with neuroendocrine dysregulation and heightened inflammatory responses, may together constitute the key mechanisms linking olfactory impairment and depressive symptoms. Interventions targeting the olfactory pathway, such as olfactory training and inhalation-based aromatherapy, have been shown to improve olfactory function and alleviate depressive symptoms to some extent. This mechanistic framework provides important theoretical support and research directions for early identification, diagnosis, and olfactory pathway-targeted intervention strategies for depressive disorders.