The more people use Facebook, the more they tend to believe that others are much happier, a new study has found.
The study by Utah Valley University found that the carefully chosen pictures of smiling, cheerful faces which Facebook users tend to plaster over their pages cumulatively convey a debilitating message to others.
Sociologists Hui-Tzu Grace Chou and Nicholas Edge interviewed 425 undergraduate students about their happiness and that of their friends.
The participants were asked how much they agreed or disagreed with statements such as "Life is fair" and "many of my friends have a better life than me".
They then described their Facebook activity including their number of "friends" and the proportion of them they actually knew.
Ninety-five percent used Facebook, and on an average they had been there for two and a half years and spent nearly five hours a week on it.
After allowing for gender, religiosity and whether people were single or attached, the study found that "the more hours people spent on Facebook, the stronger was their agreement that others were happier".
This was particularly true of Facebook users who stockpiled "friends" they did not actually know.
Those who had used Facebook for longer were also "significantly" likely to agree with the statement "life is unfair".
Conversely, the study found that people who spent more time actually socialising with friends in the flesh were less likely to feel they had been handed life's short straw.
Chou argues that this Facebook-related dissatisfaction is the result of a common psychological process known as "correspondence bias", in which one draws false conclusions about people based on limited knowledge.
"Looking at happy pictures of others on Facebook gives people an impression that others are 'always' happy and having good lives," the Daily Mail quoted Chou as saying.