Improvement of hedonic perception of odors as a marker of treatment response to escitalopram: olfactory changes through an open-label antidepressant trial

Objectives: To assess olfactory functions (threshold, identification, and hedonic valence) of depressed subjects before and after an 8-week trial of escitalopram and compare the results of responders and nonresponders.

Methods: Fifty-two depressed subjects were recruited. Participants received escitalopram and were evaluated at two visits: baseline (V0) and week 8 (V8). They were categorized as responders (Montgomery-Åsberg Depression Rating Scale [MADRS] score reduction of > 50%) or nonresponders to treatment. Participants were evaluated with the Mini International Neuropsychiatric Interview (MINI) at V0 and, at V0 and V8, completed psychometric and olfactory assessments, including MADRS and the State-Trait Anxiety Inventory (STAI), as well as the Sniffin' Sticks® test (threshold and identification tasks). The hedonic valence of smell was assessed on a 10-cm linear scale after presenting two pleasant and two unpleasant odors. Forty-three participants completed the study (24 responders and 19 nonresponders). The Mann-Whitney, chi-square, and Fisher's exact tests were used to compare olfactory, clinical, and demographic variables between groups and within the same group at V0 and V8. The Spearman coefficient was used to calculate the correlation between clinical characteristics and olfactory variables.

Results: The hedonic score of pleasant odors increased significantly between V0 and V8 only for responders (V = 61.5, p = 0.018), with no significant change in nonresponders (V = 90.5, p = 0.879). Comparison of olfactory performances between groups at V0 and V8 separately did not show a significant difference between responders and nonresponders to escitalopram. Olfactory threshold and identification scores were not different between V0 and V8 for responders or nonresponders.

Conclusion: Depressed subjects have olfactory anhedonia, which appears to regress following a positive antidepressant response. Hedonic valence may be an indicator of cognitive changes associated with depression; improvement of this valence may indicate a clinical response to antidepressants.