Depression Can Dampen Sense of Smell

BERLIN (Reuters Health) - People with serious depression seem to have an impaired ability to smell, German researchers report. Their discovery suggests there is an interaction between olfactory function and state of mind.

The work could lead to the use of smell tests to confirm depression diagnoses, or even as a diagnosis tool in people with communication difficulties, according to Dr. Bettina Pause, of Kiel University.

Pause and colleagues examined the sense of smell in 20 depressed patients being treated in hospital, and compared the results with a "control group" of 20 people who were not depressed.

The depressed patients had more difficulty picking up faint odors, even at concentrations easily detected by people in the control group.

"Compared to the control group they only began to perceive smells at higher concentrations than the control," Pause told Reuters Health.

The researchers "also conducted the tests using EEG to give an objective check," she said, and found the same reduced sensitivity to smell. "Their brains reacted later and only to stronger smells," said Pause.

The findings are to be published in March in the journal Psychophysiology.

"This is the third such study we have conducted," she said. "The results are the same and show a clear association between depression and reduced sensitivity to smell."

It's not clear why sense of smell seems to be associated with depression, according to Pause.

"I would not like to say the reduced olfactory sensitivity is the reason for the depression or the other way around but they do seem to be associated," she said. "A clue could be that the area of the brain responsible for smell and that for emotions are parallel in the brain, they are almost identical areas."

The smell sensitivity was not affected by the nature of the smell used in the tests, but Pause is also working on further experiments examining olfactory perception in people with schizophrenia.

Previous studies on schizophrenics have shown that they have confused perceptions of smell, reacting strongly to unpleasant smells but often not appreciating pleasant ones.

Other work involving people with seasonal affective disorder (SAD) has shown they have a more acute sense of smell than those without the condition, adding to the growing body of evidence of a link between olfactory function and mood.

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