title: The Association Between Olfaction and Depression: A Systematic Review.
abstract: Previous studies on the relationship between olfaction and depression have revealed mixed results. In addition, few have focused on the reciprocity of this association. The aim of this study is to combine depression and olfactory data in two separate patient populations to further understand their association. A systematic literature review was conducted using 3 online databases to identify studies correlating olfaction and depression in patients presenting with either primary depression or primary olfactory dysfunction. For the depressed population, weighted means and standard deviations for the Sniffin' Sticks Test and the 40-item Smell Identification Test were combined using 10 studies. For the olfactory dysfunction population, weighted means of Beck's Depression Inventory were combined using 3 studies. Independent t-tests were used to compare differences between groups. Comparing primary depressed patients with controls, depressed patients showed decreased scores in olfactory threshold (6.31±1.38 vs. 6.78±0.88, P = 0.0005), discrimination (12.05±1.44 vs. 12.66±1.36, P = 0.0073), identification (12.57±0.74 vs. 12.98±0.90, P < 0.0001), and 40-Item Smell Identification Test (35.31±1.91 vs. 37.41±1.45, P < 0.0001). In patients with primary olfactory dysfunction, Beck's Depression Inventory scores were significantly different between patients classified as normosmics, hyposmics and anosmics (5.21±4.73 vs. 10.93±9.25 vs. 14.15±5.39, P ≤ 0.0274 for all 3 comparisons). In conclusion, patients with depression have reduced olfactory performance when compared with the healthy controls and conversely, patients with olfactory dysfunction, have symptoms of depression that worsen with severity of smell loss.
authors.affiliation: Department of Otolaryngology-Head and Neck Surgery, Medical University of South Carolina, 135 Rutledge Ave, MSC 550, Charleston, SC 29425, USA and pkohli89@gmail.com.
authors.forename: Preeti
authors.initials: P
authors.lastname: Kohli
authors.affiliation: Department of Otolaryngology-Head and Neck Surgery, Medical University of South Carolina, 135 Rutledge Ave, MSC 550, Charleston, SC 29425, USA and.
authors.forename: Zachary M
authors.initials: ZM
authors.lastname: Soler
authors.affiliation: Department of Otolaryngology-Head and Neck Surgery, Medical University of South Carolina, 135 Rutledge Ave, MSC 550, Charleston, SC 29425, USA and.
authors.forename: Shaun A
authors.initials: SA
authors.lastname: Nguyen
authors.affiliation: Department of Otolaryngology-Head and Neck Surgery, Medical University of South Carolina, 135 Rutledge Ave, MSC 550, Charleston, SC 29425, USA and.
authors.forename: John S
authors.initials: JS
authors.lastname: Muus
authors.affiliation: Department of Otolaryngology-Head and Neck Surgery, Medical University of South Carolina, 135 Rutledge Ave, MSC 550, Charleston, SC 29425, USA and Ralph H. Johnson, VA Medical Center, 109 Bee St, Charleston, SC 29401, USA.
authors.forename: Rodney J
authors.initials: RJ
authors.lastname: Schlosser
mesh_terms: D003866:Depressive Disorder / Q000150:complications* / Q000503:physiopathology / Q000523:psychology; D006801:Humans; D000857:Olfaction Disorders / Q000150:complications* / Q000503:physiopathology / Q000523:psychology; D012684:Sensory Thresholds; D012903:Smell
keywords: BDI; SIT-40; Sniffin’ Sticks; anosmia; hyposmia; normosmia