Reduced olfactory bulb volume in depression—A structural moderator analysis

• Published in: Human brain mapping Vol. 39; no. 6; pp. 2573 - 2582
• Main Authors: Rottstädt, Fabian, Han, Pengfei, Weidner, Kerstin, Schellong, Julia, Wolff‐Stephan, Sylvia, Strauß, Timmy, Kitzler, Hagen, Hummel, Thomas, Croy, Ilona
• Format: Journal Article
• Language: English
• Published: United States John Wiley & Sons, Inc 01.06.2018; John Wiley and Sons Inc
• Subjects: Adult; Amygdala; Analysis of Variance; Brain; Brain Mapping; Case-Control Studies; Deep brain stimulation; Depression - pathology; Depression - physiopathology; Female; gray matter volume; Humans; Image Processing, Computer-Assisted; Independent variables; insula; Magnetic Resonance Imaging; Male; Mental depression; Middle Aged; Morphometry; Multiple regression analysis; Olfaction; Olfactory bulb; Olfactory Bulb - diagnostic imaging; Olfactory Bulb - physiopathology; Olfactory stimuli; Patients; Reduction; Regression Analysis; Rodents; salience; Superior temporal gyrus; Surveys and Questionnaires; Temporal cortex; Temporal gyrus; salience; gray matter volume; amygdala; insula; superior temporal gyrus
• ISSN: 1065-9471; 1097-0193; 1097-0193
• DOI: 10.1002/hbm.24024

Background Removal of the olfactory bulb (OB) leads to depression like behavior in rodents. A link between depression and olfactory function is also established in humans. We hypothesized that the human OB volume relates to depressive state and tested whether such a potential coherence is moderated by structural alterations in other brain regions. Methods Eighty‐three participants (32 patients with major depression and 51 matched healthy controls) underwent structural MR scanning. Individual OB volumes were compared between patients and controls and the impact of depression and comorbidity was analyzed with multiple regression analysis. Whole‐brain voxel‐based morphometry revealed structures co‐varying with both depressive state and OB volume. Results The OB volume of patients was significantly reduced and this reduction averaged out at 17% compared to the controls. The OB volume was correlated to the volume of the insula, superior temporal cortex, and amygdala. The independent variables of depression (β = −.37), age (β = −.25), and gender (β = −.40) explained the individual OB volume variation (R2 = .37). The correlation between OB volume and depression was moderated by volumetric reductions in a cluster including the insula and superior temporal gyrus (STG). Conclusions The OB volume relates to depression in humans and to the volume of structures which are critical for salience detection. We assume that a reduced OB volume causes diminished neural olfactory input which facilitates volume reduction in the insula and STG. The OB volume may hence constitute a factor of vulnerability to depression. Olfactory‐based deep brain stimulation is discussed as a future therapeutic approach.