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People with Depression Have Blunted Sense of Smell
by admin on: March 14th, 2011

A recent study assessed the sense of smell (olfaction) in 21 patients diagnosed with major depression. The results of this study indicated that people who suffered from major depression had a blunted sense of smell. Smell was assessed using measures of odor threshold, odor discrimination, and odor identification. In other words, people who were not depressed were able to smell the chemical used at much lower levels than depressed people.

In addition, the volume of the olfactory region of the brain (olfactory bulb) was assessed using measurements obtained from magnetic resonance (MRI) imaging. The MRI imaging demonstrated that the olfactory region (olfactory bulb volume) in the brain was smaller in patients diagnosed with major depression relative to subjects without any depressive disorder. Furthermore, statistical analysis revealed that a significant negative correlation existed between olfactory bulb volume and depression scores (as assessed using a Composite International Diagnostic Interview).

The authors of this study suggested that the decrease in the size of the olfactory areas in patients with depression were likely linked to the process of neurogenesis???the process of growth for ???new??? brain cells in this region. Previous studies have indicated that depression can inhibit neurogenesis in other brain areas, such as the hippocampus.

Of note, the patients diagnosed with major depression were medicated with selective serotonin reuptake inhibitors (Citalopram, Escitalopram, and Paroxetine), tricyclic antidepressants (Mirtazapin, Doxepin, and Primipramin), serotonin-norepinephrine reuptake inhibitors (Venlafaxin), anticonvulsants (Carbamazepin, Pregabalin, and Valproat), zinc, and lithium. In addition to the medications for depression, some patients also received narcoleptic drugs (Risperidon and Quetiapin), analgesics, and proton pump inhibitors; five patients in this group were medication-free. The authors note that the patients??? use of drugs is a limiting factor of the present study. For example, antidepressant drugs have been shown to alter gustatory (taste) function. While there is not much data linking these drugs to olfaction, it is possible that these drugs may affect a person???s sense of smell. For more information, see the August 2010 issue of the journal Neuroscience.

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