Size matters – The olfactory bulb as a marker for depression

Jin

et al. 2020

Sci Rep

We aimed to investigate the changes of olfaction of major depressive disorder (MDD) before and after medical treatment, and to preliminarily scrutinize the association between the olfactory function and the severity of depressive symptoms, response inhibition, and emotional responding. Forty-eight medicine-naïve MDD patients plus 33 healthy controls (HC) matched on gender, ages, and level of education, were recruited in the test group. The Chinese Smell Identification Test (CSIT), Self-reported Olfactory Scale (SROS), 17-item Hamilton Depression Rating Scale (HAMD-17), Hamilton Anxiety Rating Scale (HAMA), and mean reaction time/accuracy rate (ΔMRt) of emotional Stroop test were measured. The patients were assessed before the treatment (baseline) and 3 months after the treatment (follow-up). The data at the baseline level were measured then associated using multiple linear regression stepwise analysis. The MDD patients had lower scores of the CSIT and SROS and longer ΔMRt at baseline level compared to Hc while the ΔMRt of MDD patients remained longer after 3-month treatment (p's < 0.05). At the baseline level, the regression equation including age and ΔMRt of negative word-color congruent (NEG-C), was finally observed as follows: y(CSIT) = 10.676-0.063 × 1-0.002 × 2, [x 1 = the age(y), x 2 = the NEG-C (ms)]. The olfactory function of MDD appears to be correlated negatively with the age and the ΔMRT of negative stimuli before treatment. After the remission of MDD, the olfactory dysfunction was improved, which might be regarded as a responding phenotype of brain function of MDD rather than the emotional responding. Major depressive disorder (MDD) and olfaction disorder (OD) are both chronic diseases that affect human being's life quality 1. A systematic review on ten studies chosen for using the Sniffin' Sticks Test and the 40-item Smell Identification Test assessed to reveal the relationship between depression and OD. Results show that both of the olfactory threshold, olfactory discrimination, and olfactory identification were influenced by depression 2. Furthermore, symptoms of depression worsen with the severity of olfactory loss 3. It was demonstrated that olfactory bulbectomy, as a well-known method, could induce an animal model of depression in animal experiment 4. In depression-related brain areas including hippocampus, frontal cortex and hypothalamus, the turnover of serotonin and dopamine decreases in the olfactory bulbectomized rats 5. Similarly, in human studies, Cory et al. 6 found that patients with depression have decreased activities in the left medial orbitofrontal cortex (OFC) accompanied with the defect of the olfactory identification. However, Zucco et al. 7 argued that the changes mentioned above occur in patients with the MDD only, not with the mild or moderate depressive disorder. In the neural circuits involved in emotional processing 8 , these key structures such as amygdala, hippocampus, anterior cingulate cortex(ACC) and OFC, are the imperative functional regions of the human olfactory map...

Section: Discussionmentioning

confidence: 99%

Association between olfactory function and inhibition of emotional competing distractors in major depressive disorder

Jin

et al. 2020

Sci Rep

“…However, these findings cannot be replicated in humans. Nevertheless, studies showed that olfactory bulb volume differs significantly between depressed and non-depressed individuals and seems to be a promising marker for depression [ 16 ]. Fifth, stress, a triggering factor of depression in vulnerable subjects, induces behavior similar to some symptoms of depression, as well as decreased cell proliferation or neurogenesis, both in the hippocampus and in the olfactive bulbs [ 17 ].…”

Section: Introductionmentioning

confidence: 99%

Depression, Olfaction, and Quality of Life: A Mutual Relationship

et al. 2018

Olfactory dysfunction has been well studied in depression. Common brain areas are involved in depression and in the olfactory process, suggesting that olfactory impairments may constitute potential markers of this disorder. Olfactory markers of depression can be either state (present only in symptomatic phases) or trait (persistent after symptomatic remission) markers. This study presents the etiology of depression, the anatomical links between olfaction and depression, and a literature review of different olfactory markers of depression. Several studies have also shown that olfactory impairment affects the quality of life and that olfactory disorders can affect daily life and may be lead to depression. Thus, this study discusses the links between olfactory processing, depression, and quality of life. Finally, olfaction is an innovative research field that may constitute a new therapeutic tool for the treatment of depression.

“…This study was embedded in a larger design (for complete Methods and Materials information please compare; Rottstaedt et al, 2018 ). Of the patient cohort investigated there, only patients with diagnosed Major Depression ( n = 73, all inpatients of the Department of Psychosomatic and Psychotherapy of the Dresden University Hospital) were included in this investigation.…”

Section: Methodsmentioning

confidence: 99%

“…Similar to aging, the typical GM reduction patterns in depression especially concern the hippocampus and prefrontal cortex (Bora et al, 2012 ; Sacher et al, 2012 ; Singh et al, 2013 ). Interestingly, depression is also related to premature reduction of OB volume (Negoias et al, 2010 ; Croy et al, 2013 ) which was suggested as biological marker for the disease (Kohli et al, 2016 ; Croy and Hummel, 2017 ; Rottstaedt et al, 2018 ). We hence aimed to investigate the association of OB volume decline with age in healthy controls and depressed patients.…”

Section: Introductionmentioning

confidence: 99%

Pre-aging of the Olfactory Bulb in Major Depression With High Comorbidity of Mental Disorders

Rottstaedt¹,

Weidner²,

Hummel³

2018

Front. Aging Neurosci.

Recent studies suggest that accelerated aging of the brain is a neuroanatomical signature of the state of mental diseases. In major depression, this pre-aging effect is negatively associated with the duration since the first onset of the disease. The olfactory bulb (OB) shrinks with age in healthy subjects and patients with mental diseases show reduced OB volumes, especially those with major depression. It is unclear whether this OB reduction in mental diseases resembles a pre-aging process and whether it is associated to the duration since the onset of the mental disease. To this aim, we investigated OB volume in 73 patients (mean-age 40.4 years, SD = 12.1 years, 57 women) with major depression and mixed comorbid mental diseases (diagnoses ranged from 1 to 6, median: 3) and 51 healthy controls (mean-age 39.2 years, SD = 13.0 years, 26 women) matched for age and sex. Patient’s first onset of disease ranged from 15 to 53 years (mean 24.2 years). All participants underwent structural MR imaging with a spin-echo T2-wheighted sequence covering the anterior and middle segments of the skull base. All results were corrected for total intracranial volume (TIV) and sex. Individual OB volume was calculated by planimetric manual contouring and the pronounced diameter change in transition from bulb to tract was used as the distal demarcation of the OB. Inter-rater correlation between two independent persons analyzing the data was high (IRC = 0.81, p < 0.005). An age-dependent decline of the OB volume was confirmed in healthy controls (r = −0.34, p < 0.05). However, this pattern was altered in patients where the OB volume was not related to age, but to the duration since the onset of the mental disease (r = −0.25, p < 0.05). This association remained stable when controlling for age. Additionally, analyses of age sub-groups revealed that the association between duration since the onset of the mental disease and OB volume was mainly driven by the group aged 50 years and above (r = −0.68; p < 0.01). We conclude that there are time windows where the OB volume is susceptible for the effects of a mental disease, e.g., depression. These effects result in cumulative pre-aging in the OB in older patients with mental diseases.