L’smella marker of the depression ? Patients suffering from depression would have difficulty in smelling pleasant odors. The researchers also found that in addition to being a disease marker, these olfactory disorders could also be a sign of relapse. “People with severe depression have difficulty experiencing pleasure. In addition, the area of the brain involved in the pleasant sensation caused by odors is dysfunctional in these people, explains in a press release Catherine Belzung, co-author of this published work. by the National Institute of Health and Medical Research (Inserm).
To study this interaction between the sense of smell and depression, the researchers performed olfactory tests on 18 people hospitalized for an episode of severe depression. Their results were compared with those of 54 healthy volunteers.
In all, the participants breathed in eight different smells, sometimes pleasant (almonds, vanilla), sometimes repulsive (vomit, rancid cheese). These smells 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 recognize odors mixed with others less well. And especially the pleasant smells were not identified by the patients. “Surprisingly, vanilla, cinnamon or bitter almond were classified as unpleasant smells,” Ms Belzung added.
At the end of the consultation, the depressed patients began antidepressant treatment for a period of six weeks, but this did not correct their olfactory disturbances. “Only one smell had become pleasant again for the majority of them. It is a smell linked to memories and childhood: that of the small pot of glue used in class which smelled slightly of bitter almond”, according to Ms. Belzung.
The researchers will now determine whether the smell disorder is a specific marker of depression or whether 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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