THOSE who have resisted the urge to join Facebook will surely feel vindicated when they read the latest research. A study just published by the Public Library of Science, conducted by Ethan Kross of the University of Michigan and Philippe Verduyn of Leuven University in Belgium, has shown that the more someone uses Facebook, the less satisfied he is with life.

Past investigations have found that using Facebook is associated with jealousy, social tension, isolation and depression. But these studies have all been “cross-sectional”—in other words, snapshots in time. As such, they risk confusing correlation with causation: perhaps those who spend more time on social media are more prone to negative emotions in the first place. The study conducted by Dr Kross and Dr Verduyn is the first to follow Facebook users for an extended period, to track how their emotions change.

The researchers recruited 82 Facebookers for their study. These volunteers, in their late teens or early 20s, agreed to have their Facebook activity observed for two weeks and to report, five times a day, on their state of mind and their direct social contacts (phone calls and meetings in person with other people). These reports were prompted by text messages, sent between 10am and midnight, asking them to complete a short questionnaire.

When the researchers analysed the results, they found that the more a volunteer used Facebook in the period between two questionnaires, the worse he reported feeling the next time he filled in a questionnaire. Volunteers were also asked to rate their satisfaction with life at the start and the end of the study. Those who used Facebook a lot were more likely to report a decline in satisfaction than those who visited the site infrequently. In contrast, there was a positive association between the amount of direct social contact a volunteer had and how positive he felt. In other words, the more volunteers socialised in the real world, the more positive they reported feeling the next time they filled in the questionnaire.

A volunteer’s sex had no influence on these findings; nor did the size of his (or her) social network, his stated motivation for using Facebook, his level of loneliness or depression or his self-esteem. Dr Kross and Dr Verduyn therefore conclude that, rather than enhancing well-being, Facebook undermines it.

Their study does not tease out why socialising on Facebook has a different effect from socialising in person. But an earlier investigation, conducted by social scientists at Humboldt University and Darmstadt’s Technical University, both in Germany, may have found the root cause. These researchers, who presented their findings at a conference in Leipzig in February, surveyed 584 users of Facebook aged mostly in their 20s. They found that the most common emotion aroused by using Facebook is envy. Endlessly comparing themselves with peers who have doctored their photographs, amplified their achievements and plagiarised their bons mots can leave Facebook’s users more than a little green-eyed. Real-life encounters, by contrast, are more WYSIWYG (what you see is what you get).

What neither study proves is whether all this is true only for younger users of Facebook. Older ones may be more mellow, and thus less begrudging of their friends’ successes, counterfeit or real. Maybe.