Olfactory markers for depression: Differences between bipolar and unipolar patients

Abstract

The aim of the study was to compare olfactory functions between unipolar and bipolar patients according to the thymic states (depressed, euthymic) and determine specific olfactory variations between these different states. Methods We recruited 176 participants in 5 groups: depressed bipolar (DB), euthymic bipolar (EB), depressed unipolar (DU), euthymic unipolar (EU), and controls (HC). They were assessed using the Sniffin' sticks threshold and identification tests. Odors' pleasantness, intensity, familiarity and emotion were assessed. Clinical evaluation explored dimensions of depression, mania, anxiety, and anhedonia. Results Smell identification was lower in DU compared to EU patients and controls. Pleasant odors received lower hedonic rating in DU and DB patients compared to EU and EB patients respectively. Negative correlation was found in EB patients between hedonic rating and social anhedonia. In EU patients hedonic rating was negatively correlated with anxietystate, and anhedonia. Conclusions Odor identification of pleasant odors is altered in both depressive states. Only unipolar patients would recover a regular identification level in symptomatic remission, while bipolar subjects would keep their deficits. Hedonic rating is lower in bipolar depressed patients compared to unipolar ones, and these deficits improve after remission. Hedonic rating of pleasant odors may distinguish bipolar depression from unipolar depression during periods of decompensation and phases of remission. Olfactory assessment may be useful to screen unipolar and bipolar depression, leading to possible future sensory markers in mood disorders.

Association between chemosensory impairment with neuropsychiatric morbidity in post-acute COVID-19 syndrome: results from a multidisciplinary cohort study

“…Noteworthy, regarding the impact of chemosensory deficits on mental health, even though we found associations between smell and taste alterations with psychiatric diagnoses (mostly anxiety and common mental disorders), the statistical significance of these associations was not sustained upon multivariate analysis. Previous studies suggested a link between hyposmia/anosmia and the development of major depressive disorder [ 46 – 51 ], but apparently individuals with unipolar depression tend to recover their olfactory function after symptomatic remission, contrary to individuals with bipolar depression [ 52 ]. Neuroimaging studies suggested that smaller volumes of the olfactory bulb could be associated with depression [ 53 , 54 ].…”

Spanish Validation for Olfactory Function Testing Using the Sniffin’ Sticks Olfactory Test: Threshold, Discrimination, and Identification

“…While vision and hearing have been treated as basic senses for general health, smell is gaining increasing interest in clinical and research settings, as more and more pathologies are associated with 2 of 19 altered smell. Some examples are diabetes mellitus [18,19], rhinitis, sinusitis [20,21], anxiety [22,23], major depression [24][25][26][27], schizophrenia [28], autism [29], liver disease [30,31], arterial hypertension [32], and neurodegenerative diseases [33,34], such as frontotemporal dementia [35][36][37] and amyotrophic lateral sclerosis [38]. More recently, a plethora of scientific evidence indicates that deterioration of smell is a biological marker in the preclinical phase of neurodegenerative diseases, such as Parkinson's disease [39][40][41][42] or Alzheimer's disease [43][44][45].…”

Transcriptome Changes in Three Brain Regions during Chronic Lithium Administration in the Rat Models of Mania and Depression

“…Moreover, previous study showed that olfactory bulbectomy induced depressive-like behavior in rodents [ 19 ], in particular when taking into account the close anatomical links between the olfactory system and the brain circuits involved in memory [ 20 ] and emotion [ 21 ]. The recent studies reported the presence of sensory changes during mood swings in BD [ 22 ] and that olfactory assessment may be useful to screen unipolar and bipolar depression [ 23 ]. These genes involved in olfactory receptors activity were also differentially expressed in either manic and depressive rats responding to chronic lithium treatment and showed the opposite effect that also depended on tissue: in the amygdala they were upregulated after chronic lithium in mania, but downregulated in depression; in the hippocampus they showed downregulated expression in mania, but upregulated in depression after chronic lithium.…”