Depression suppresses the sense of smell

Research by German scientists has shown that the part of the brain responsible for smell is smaller in people with depression. They have a significantly poorer sense of smell than healthy individuals. This finding helps explain why many mental disorders, such as depression, schizophrenia, and seasonal affective disorder, impair the sense of smell. Measurements of the olfactory bulb will allow for better monitoring of the effectiveness of depression treatments. To reach this conclusion, researchers from the University of Dresden exposed 21 people—21 with severe depression and 21 who were healthy—to a faintly odorous chemical. They gradually increased the odor's concentration until the volunteers were able to detect it. The level of depression affects the size of the olfactory bulb The researchers also measured the volunteers' olfactory bulbs—the part of the brain that allows us to sense smells. They used magnetic resonance imaging (MRI). Healthy individuals were able to detect the substances' odors at significantly lower levels than the depressed participants. Furthermore, those with depression also had smaller olfactory bulbs—an average of 15%. The researchers concluded that the more severe the depression, the smaller the olfactory bulb. Antidepressant medication did not affect the study results. Olfactory bulb size and depression are likely linked to the process of neurogenesis, which is responsible for the growth of new brain cells. Depression is known to inhibit neurogenesis in brain regions such as the hippocampus. People with depression often have low levels of neurotrophic factor, which stimulates neurogenesis.