LONDON: Witnessing friends' vacations, love lives and work successes on Facebook can cause envy and trigger feelings of misery and loneliness, according to German researchers.

A study conducted jointly by two German universities found rampant envy on Facebook, the world's largest social network that now has over one billion users and has produced an unprecedented platform for social comparison.

The researchers found that one in three people felt worse after visiting the site and more dissatisfied with their lives, while people who browsed without contributing were affected the most.

"We were surprised by how many people have a negative experience from Facebook with envy leaving them feeling lonely, frustrated or angry," researcher Hanna Krasnova from the Institute of Information Systems at Berlin's Humboldt University told Reuters.

"From our observations some of these people will then leave Facebook or at least reduce their use of the site," said Krasnova, adding to speculation that Facebook could be reaching saturation point in some markets.

Researchers from Humboldt University and from Darmstadt's Technical University found vacation photos were the biggest cause of resentment with more than half of envy incidents triggered by holiday snaps on Facebook.

Social interaction was the second most common cause of envy as users could compare how many birthday greetings they received to those of their Facebook friends and how many "likes" or comments were made on photos and postings.

"Passive following triggers invidious emotions, with users mainly envying happiness of others, the way others spend their vacations and socialize," the researchers said in the report "Envy on Facebook: A Hidden Threat to Users' Life Satisfaction?" released on Tuesday.

"The spread and ubiquitous presence of envy on Social Networking Sites is shown to undermine users' life satisfaction."

They found people aged in their mid-30s were most likely to envy family happiness while women were more likely to envy physical attractiveness.

These feelings of envy were found to prompt some users to boast more about their achievements on the site run by Facebook Inc. to portray themselves in a better light.

Men were shown to post more self-promotional content on Facebook to let people know about their accomplishments while women stressed their good looks and social lives.

The researchers based their findings on two studies involving 600 people with the results to be presented at a conference on information systems in Germany in February.

The first study looked at the scale, scope and nature of envy incidents triggered by Facebook and the second at how envy was linked to passive use of Facebook and life satisfaction.

The researchers said the respondents in both studies were German but they expected the findings to hold internationally as envy is a universal feeling and possibly impact Facebook usage.

"From a provider's perspective, our findings signal that users frequently perceive Faceook as a stressful environment, which may, in the long-run, endanger platform sustainability," the researchers concluded.