Many adults eat too much salt
Scientists suggest we may add extra salt to our food because it boosts our mood, even though we know too much is bad for us.
University of Iowa researchers writing in Psychology and Behavior say salt may act as a natural antidepressant.
Tests on rats found those with a salt deficiency shied away from activities they normally enjoyed - a sign of depression.
But experts warn eating too much salt is linked to high blood pressure.
The body needs sodium - which along with chloride makes up salt - to function, but having too much and raising blood pressure is linked to an increased risk of stroke and heart attack.
The UK's Food Standards Agency says the average adult should eat no more than 6g of salt a day.
Intake is falling, but last year the average was 8.6g. Around three-quarters of the salt we eat comes in pre-prepared foods.
The findings are published as the FSA renewed its advice for people to eat more healthily.
It backed an independent panel of experts warning that celebrity chefs were promoting high-fat recipes, and contributing to the obesity crisis.
The tests carried out by US researchers found that when rats were deficient in salt, they shy away from activities they normally enjoy, like drinking a sugary substance or pressing a bar that stimulates a pleasant sensation in their brains.
Psychologist Kim Johnson, who led the research, said: "Things that normally would be pleasurable for rats didn't elicit the same degree of relish, which leads us to believe that a salt deficit and the craving associated with it can induce one of the key symptoms associated with depression."
She said it a loss of pleasure in normally pleasing activities is one of the most important features of psychological depression.
And she said there were signs salt could be addictive.
One sign of addiction is using a substance even when it is known to be harmful - and even though people know they should cut their salt intake, they like the taste and find low-salt foods bland so continue to eat it.
Another strong aspect of addiction is the development of cravings if something is withheld.
The University of Iowa team say tests they carried out showed similar changes in brain activity whether rats are exposed to drugs or salt deficiency.
"This suggests that salt need and cravings may be linked to the same brain pathways as those related to drug addiction and abuse."
But a spokesman for Consensus Action on Salt and Health (CASH), which campaigns to raise awareness about the health risks of eating too much salt, said: "Our bodies need a very small amount of salt to function, but nothing like the quantities that most of us eat.
"This research may help us to understand why some people still eat too much salt, even though they know it's bad for them.
"I personally have never felt depressed by not eating too much salt: I think it would be far more depressing to have a heart attack or stroke that could have been avoided by not eating so much salt."