The influence of olfactory training on depressive symptoms and olfactory function in patients with olfactory dysfunction – A prospective observational pilot study

• There is a high prevalence of depressive symptoms in patients with olfactory dysfunction. • There is no correlation between the severity of depressive symptoms and the severity of olfactory dysfunction. • Our study shows a decline of depressive symptoms at follow-up but no significant change in olfactory function. • There is insufficient evidence for using olfactory training as treatment for depressive symptoms. We hypothesize a reduction of depressive symptoms due to spontaneous remission. Olfaction plays an important role in different aspects of our daily functioning and there is a positive correlation between olfactory dysfunction (OD) and depressive symptoms. Multiple parts of the brain are involved in both olfaction and the origin of depressive symptoms, e.g. amygdala and hippocampus. Olfactory training (OT) is one of the main therapeutic options in the management of OD. The objective of our study is to look at the prevalence of depressive symptoms in patients with olfactory disorders and to examine the effect of OT on mood in patients who present with OD. We included patients who presented at the Ears-Nose-Throat outpatient clinic with subjective OD and were eligible for OT. At baseline and follow-up (3 to 6 months) olfactory function and depression were assessed respectively by a Sniffin’ Sticks test and the Quick Inventory of Depressive Symptoms questionnaire. Our study revealed that 57 % of participants had mild to severe depressive symptoms at baseline. There was no correlation between the depressive symptoms and OD at baseline. From baseline to follow-up, there was a significant decline in depressive symptoms, but no significant changes in the olfactory function. In addition, there was no correlation between change in depression and change in olfactory function. These results should be interpreted with caution because this is an observational pilot study with no placebo-controlled group and a small sample size. Further investigation is warranted.