Facebook is a habit-forming activity - but users who spend a lot of time on the site say they feel less happy with their lives.
University of Gothenburg researchers say that many users log in as soon as they turn their PCs on - and that the behaviour can develop into an 'addiction'.
People in low income groups and the poorly educated are particularly at risk.
Up to 85% of users say that they use Facebook daily - and half say they start up Facebook as soon as they open their web users.
Half fear that they are not 'on top of things' if they are not logged into the site, and 25% say they fill 'ill at ease' if they can't log in regularly.
The Swedish survey, which polled 1,000 people aged 18-73 showed the network had its dark side.
'Facebooking may become an unconscious habit. A majority of the respondents log in every time they start their web browser. This may even develop into an addiction,' says Leif Denti, doctoral student of Psychology at the University of Gothenburg.
People with low income and low-educated individuals spend more time on Facebook.
Women are generally more active than men on Facebook.
Users with low income and low education use Facebook more than other groups. Within these groups, users who spend more time on Facebook also report feeling less happy and less content with their lives.
This relationship is also present for women, but not for men.
The other surprise about the network is that although a huge amount of personal 'news' is traded, through the site, it tends to focus purely on the positive.
'Facebook is a social tool that is clearly used to manage relationships with friends and family.
'But users won't write just anything – most of the content they share has something to do with major events, positive events and when feeling good. Only 38 percent write about negative emotions and events,' says Leif Denti.