 Losing our sense of taste may be an early sign of depression, say scientists.
Taste is linked to the brain chemicals which control our moods, a study found.
When levels of these chemicals fall, which is thought to happen when a patient is suffering depression, our sense of taste is blunted.
But boosting levels of the mood-enhancing chemicals serotonin and noradrenaline improves sense of taste, according to the researchers.
The team from Bristol University say their findings could explain why loss of appetite often goes hand-in-hand with depression.
Their discovery could lead to the development of a taste test allowing doctors to quickly and accurately choose the right drug to treat a patient's depression.
The study looked at the relationship between serotonin and noradrenaline and sense of taste. Volunteers were asked to taste a range of foods and their ability to pick up different tastes was rated.
They were then given antidepressants which raise the levels of serotonin or noradrenaline.
The results showed that raising serotonin levels enhanced their ability to recognise bitter and sweet tastes. Raising noradrenaline levels made them more sensitive to bitter and sour tastes.
Some anti-depressants such as Prozac raise serotonin levels. Edronax increases the amount of noradrenaline. Other drugs can improve levels of both chemicals.
Doctors currently have no way of knowing which medicine will work for which patient and often initially prescribe the wrong drug.
Being able to pinpoint the right drug early on would enhance recovery from the condition that affects one in five Britons at some point in their lifetime.
A taste test of this kind could be available within three to seven years, say experts.
Researcher Dr Jan Melichar 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 to 80 per cent of the time. It then takes up to four weeks to see if the drug is working, or if we need to change it. But with a taste test, we may be able to get it right first time."
Dr Melichar, a psychiatrist, said: "If you can get people back to being well quicker, that is something fantastic."
The research, which is published in the Journal Of Neuroscience, could also lead to treatments for conditions such as obesity.
"It could be that some part of comfort eating is because you are eating more to get the same taste because your taste has blunted," said Dr Melichar.
"So, if you could somehow improve people's sense of taste, they might eat less."
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Director: Liu Chi