THE’smell, a marker of the depression ? Patients with depression are said to have difficulty smelling pleasant smells. The researchers also found that in addition to being a disease marker, these olfactory disorders could also constitute a sign of relapse. “People with severe depression have difficulty experiencing pleasures. In addition, the area of the brain involved in the pleasant sensation caused by odors presents dysfunctions in these people, explains in a press release Catherine Belzung, co-author of this published work. by the National Institute for Health and Medical Research (Inserm).
To study this interaction between smell and depression, the researchers gave olfactory tests to 18 people hospitalized for an episode of severe depression. Their results were compared with those of 54 healthy volunteers.
In all, the participants inhaled eight different smells, sometimes pleasant (almonds, vanilla), sometimes repulsive (vomit, rancid cheese). These odors were sometimes mixed, which “corresponds more to the perception of everyday smells”, specifies Catherine Belzung.
As a result, depressed patients are less able to distinguish between different levels of odor intensity. They are less able to recognize odors mixed with others. And especially the pleasant smells were not identified by the patients. “Surprisingly, vanilla, cinnamon or bitter almond were classified as unpleasant odors,” Ms. Belzung added.
At the end of the consultation, the depressed patients began an antidepressant treatment lasting six weeks, but this did not correct their olfactory disturbances. “Only one odor had become pleasant again in the majority of them. It is an odor linked to memories and childhood: that of the little pot of glue used in class which smelled slightly of bitter almond”, according to Ms. Belzung.
Researchers will now determine if the smell disorder is a specific marker for depression or if it is also present in patients with other psychiatric and neurological conditions. A trial is underway in Alzheimer’s disease and in alcohol-dependent patients.
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