Taste test may help identify best depression treatments

New research has indicated that it may be possible to use taste to determine whether someone is depressed, and as a way of determining which is the most suitable drug to treat their depression.

University of Bristol research has found that our ability to recognize certain flavors can be improved with drugs normally prescribed for depression.

Researchers gave healthy volunteer subjects antidepressants that increase levels of the neurotransmitters serotonin and noradrenaline. They report that these tests resulted in the participants being able to detect different tastes (sugar, sour, salt, and bitter) at lower concentrations, thus enhancing their ability to taste.

Dr. Lucy Donaldson, the study’s senior author, said: “When we increased serotonin levels we found that people could recognize sweet and bitter taste and much lower concentrations than when their serotonin levels were normal. With increased noradrenaline levels the same people could recognize bitter and sour tastes at lower concentrations. Salt taste doesn’t seem to be affected at all by altering either of these neurotransmitters.”

She added, “Because we have found that different tastes change in response to changes in the two different neurotransmitters, we hope that using a taste test in depressed people will tell us which neurotransmitter is affected in their illness.

Dr. Jan Melichar, the paper’s lead psychiatrist, called the findings “very exciting,” and said, “Until now we have had no easy way of deciding which is the best medication for depression. As a result, we get it right about 60-80% of the time. It then takes up to four weeks to see if the drug is working, or if we need to change it. However, with a taste test, we may be able to get it right first time.”

Oftentimes, taste is believed to be genetically determined, and, until now, people assumed it was fixed throughout life. But these studies show that the ability to recognize different tastes can be altered by the neurotransmitters serotonin and noradrenaline and by people’s mood.

In the study, three drugs were administered to the subjects: SSRI (selective serotonin reuptake inhibitor) to raise serotonin levels; NARI (noradrenaline reuptake inhibitor) to raise noradrenaline levels; and an inactive placebo.

The participants in the study were first tested for their ability to recognize certain tastes. The drug was then given to them and two hours afterward they were asked to repeat the taste test.

The volunteers were also assessed for their anxiety levels, their overall level of anxiety being related to their ability to taste – the more anxious they were, the less sensitive to bitter and salt tastes they were.

These results provide important insights into how neurotransmitters affect our taste system. It seems that tasting bitter things can be changed by alterations in both noradrenaline and serotonin levels, that sweet taste is affected by only serotonin levels, and that sour taste is affected by noradrenaline.

The findings may also explain why anxious and depressed people have diminished appetite. The results show that taste is related to anxiety levels, even in generally well individuals.

The findings appear in the December 6, 2006 issue of the Journal of Neuroscience.

SOURCES: Donaldson L, Melichar J. University of Bristol, Bristol, UK.

© Copyright 2007 Insight Journal Online Magazine.

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