"That is not what we expected," Mann says. "We kept repeating the study, because we didn't believe it."
In another experiment, Mann had half the kids eat comfort food, and the other half eat nothing. After a few minutes, both groups felt equally better. The comfort food had no effect on mood.
The results of these experiments appeared in the August issue of Health Psychology. "People are taking this very hard," Mann says. "I guess it removes a very handy justification people have for eating comfort food."
Of course, the study has a few significant limitations. For one, it only looked at a particular kind of negative mood — induced by watching sad films. Other studies have come to different conclusions. For example, one in 2011, published in the journal Psychological Science, suggested that eating chicken soup may help some feel less lonely.
And the researchers didn't look at the real-life contexts in which people eat comfort foods. "Maybe the comfort from comfort food comes from going to a cafe acquiring it," Mann says. The research on the psychological effects of comfort food is fairly scant, she notes, so we don't have any definite answers yet.
David Levitsky, a professor of nutrition at Cornell University, says Mann's research is in line with what he would have expected. "We tend to look for a magic solution to our problems," Levitsky says.
The idea that we can feel better by simply consuming certain foods is very appealing, he says, "but in actuality, feeling better has nothing to do with the food itself, and it's a very weak psychological effect."
The comfort foods we turn to the most are the ones we ate while growing up, or the ones that remind us of celebrations, Levitsky says. We may associate chicken soup with all those times Mom took care of us when were little, and maybe mashed potatoes remind us of joyful Thanksgivings. It's a connection between food and memory beautifully rendered in this scene from the movie Ratatouille, when a crusty food critic finds his meal transportive:
We think that eating foods that remind us of home, or of good times, will make us feel better when we're down, Levitsky says. "But we don't know if it's performing the function that people want it to."
So does this mean we should step away from the Ben and Jerry's when we're feeling sad? Not necessarily, Levitsky says. "There's no harm to it," he says, unless you're overeating, or consistently eating food to avoid coping with big problems.
Mann concurs. "I am not opposed to comfort food-eating during your occasional glum moment," she says.
Maybe the food doesn't help anything, she says, but that doesn't mean it isn't delicious. "So you lose one justification for eating a cookie. Come up with another one."
Maanvi Singh is a freelance science and health writer based in Washington, D.C.
Copyright 2014 NPR.