Background: Here, we refer to our publication “Symptoms of depression change with olfactory function” [Sci Rep. 2022 Apr 5;12(1):5656]. Objectives: Depression decreases with olfactory improvement, but the question remains open of whether patients who indicate more suffering regarding mood impairment exhibit a different pattern of recovery from olfactory loss compared to those who suffer less. Method: In the course of an additional investigation of our previously published dataset, we established groups of participants (N = 171) with low (≤8 points on a depression [ADSL] scale; 47%; n = 45) and high (≥14 points on ADSL scale; 53%; n = 53) mood impairment. Results: We found that the group that reported more sufferance on a depression [ADSL] scale improved more in change of olfactory function, and, more importantly, odor discrimination change over a period of an average of 11 months. Conclusion: Patients, who suffered more, as indicated by higher scores on ADSL scale, may have been more willing to commit to the study protocol, and thus their improvement was more notable.

Here, we refer to our publication “Symptoms of depression change with olfactory function” [1]. Olfaction is well-established to be linked to depression severity [2‒5] and to increase when patients improve in depression score; i.e., get healthier [6]. However, the question remains open of whether patients who indicate more suffering regarding mood impairment exhibit a different pattern of recovery from olfactory loss compared to those who suffer less.

In the course of an additional investigation of our previously published dataset, assuming a leptokurtic data distribution (greater number of variations in the tails of data on both sides of the information’s peak), we established groups of participants (N = 171) with low (≤8 points on a depression [ADSL] scale; 47%; n = 45) and high (≥14 points on ADSL scale; 53%; n = 53) mood impairment. Different etiologies of olfactory loss were present such as idiopathic, postviral, sinonasal, etc. Detailed characteristics of both groups in terms of baseline olfactory scores, causes of olfactory dysfunction, and its duration are described in Table 1.

Data Analysis

We ran a series of t tests to examine whether both groups differ in terms of olfactory improvement following treatment over a period of an average of 11 months. All the analyses were additionally supported with Bayesian statistics [7].

We found that both groups differed significantly in change of olfactory function (TDI change: t = 2.4, p = 0.021, Cohen’s d = 0.5; Fig. 1a), and, more importantly, odor discrimination change (D change: t = 2.4, p = 0.017, Cohen’s d = 0.5; Fig. 1b). In both cases, the group that indicated more sufferance improved more while no such effect was noted in odor threshold or identification. Also, Bayesian statistics confirmed these results, particularly for odor discrimination change (B10 = 2.8; for TDI change: B10 = 2.4), showing additionally that the other components did not differ between the groups (for T change: B01 = 3.4; for I change: B01 = 4.1).

To conclude, the present data indicate that participants who declared more sufferance improved more, particularly in terms of odor discrimination change but also overall olfactory functions, compared to those who declared less sufferance. We suggest that the patients, who suffered more, as indicated by higher scores on ADSL scale, were more willing to commit to the study protocol, and thus their improvement was more notable. So far, no data support such an explanation, but intuitively, experiencing higher mood-related sufferance may lead patients who were already motivated enough to come to the clinic to be actively involved in therapeutic procedures. However, one should notice that the difference between both groups was not immense and required establishing specific division criteria to be thoroughly investigated. In this context, future studies should further examine whether, in clinical practice, the likelihood of recovery is higher in more severely depressed patients compared to those less depressed. If confirmed, the mood effect could be treated as a prognostic factor for recovery.

The retrospective study was performed according to the principles of the Declaration of Helsinki on biomedical research involving human subjects. It was approved by the Ethics Committee at the Medical Faculty of the TU Dresden (EK number 251112006) covering anonymized retrospective and pooled analyses. All participants consented to the examinations.

The authors have no conflicts of interest to declare.

No funding was received.

A.S.: data analysis, writing, and critical review. T.H.: conceptualization, supervision, and critical review.

All data generated or analyzed during this study are included in this article. Further inquiries can be directed to the corresponding author.

1.
Sabiniewicz
A
,
Hoffmann
L
,
Haehner
A
,
Hummel
T
.
Symptoms of depression change with olfactory function
.
Sci Rep
.
2022 Apr 5
12
1
5656
.
2.
Atanasova
B
,
Graux
J
,
El Hage
W
,
Hommet
C
,
Camus
V
,
Belzung
C
.
Olfaction: a potential cognitive marker of psychiatric disorders
.
Neurosci Biobehav Rev
.
2008 Sep 1
32
7
1315
25
.
3.
Chen
B
,
Benzien
C
,
Faria
V
,
Ning
Y
,
Cuevas
M
,
Linke
J
et al
.
Symptoms of depression in patients with chemosensory disorders
.
ORL J Otorhinolaryngol Relat Spec
.
2021 Mar
83
3
135
43
.
4.
Croy
I
,
Hummel
T
.
Olfaction as a marker for depression
.
J Neurol
.
2017 Apr
264
4
631
8
.
5.
Kim
BY
,
Bae
JH
.
Olfactory function and depression: a meta-analysis
.
Ear Nose Throat J
.
2022 Mar 31
014556132110565
.
6.
Leon
M
,
Woo
CC
.
Olfactory loss is a predisposing factor for depression, while olfactory enrichment is an effective treatment for depression
.
Front Neurosci
.
2022
;
16
:
1013363
.
7.
Dienes
Z
.
Using Bayes to get the most out of non-significant results
.
Front Psychol
.
2014 Jul 29
5
781
.