When people force themselves to smile because they hope to feel better or they do it just to hide their negative emotions, this strategy may backfire, researchers said.
"Most commonly, people smile when they are happy, because smiling reflects happiness," said Anirban Mukhopadhyay, an associate professor of marketing at Hong Kong University of Science and Technology.
"However, people also smile when they are unhappy, to mask negative emotion or to try and become happy," he said.
In the latter scenario, people may associate the acts of smiling not only with feeling happy, but also with feeling unhappy, he added.
In one experiment, 108 people completed surveys asking them how frequently they smiled on the day of the experiment and whether they thought that people usually smile to feel good or to force themselves to feel good, 'Live Science' reported.
The participants also completed questionnaires that examined how satisfied they were with their lives.
In another experiment, the researchers recruited a group of 63 people and showed them funny pictures. They asked the participants to smile if they actually found the pictures funny.
And, in the third experiment, the researchers asked 85 people to list situations in which they smiled because they felt happy.
The investigators asked the participants to perform facial muscular exercises in which they were told to manipulate their facial muscles to create a smilelike or non-smilelike shape. Then they examined the participants' level of life satisfaction.
When the researchers analysed the results of the three experiments, they concluded that those people in the study who did not typically smile when they were happy felt worse when they smiled frequently, whereas the people who often smiled when they were happy felt better when they smiled frequently.
"More generally, we think that making people who are feeling bad smile could backfire and make them feel worse, because they may interpret smiling as trying to become happy," Mukhopadhyay said.
"Smiling frequently would remind them of being not happy," he said, advising that the best strategy in such cases may in fact be not to smile until the negative emotion that is making a person feel bad gets resolved.
The study was published in the Journal of Experimental Social Psychology.