The more Facebook friends you've got, the more likely you are to feel stressed out by the site, say psychologists from Edinburgh Napier University.
After quizzing around 200 students on their Facebook use, they concluded that for many users the negative effects of Facebook outweighed the benefits of staying in touch with friends and family.
"Although there is great pressure to be on Facebook there is also considerable ambivalence amongst users about its benefits," says Dr Kathy Charles, who led the study.
"Our data also suggests that there is a significant minority of users who experience considerable Facebook-related anxiety, with only very modest or tenuous rewards. “And we found it was actually those with the most contacts, those who had invested the most time in the site, who were the ones most likely to be stressed."
The 12 per cent of respondents who said that Facebook made them feel anxious turned out to have an average of 117 'friends' each. The remaining 88 percent, who said that Facebook didn't stress them, had an average of 75 'friends' each.
Many users said they were anxious about withdrawing from the site for fear of missing important social information or offending contacts. Other causes of tension included getting rid of unwanted contacts, the pressure to be inventive and entertaining, and coping with different etiquette for different friends.
"The other responses we got in focus groups and one-to-one interviews suggests that the survey figures actually under represent aspects of stress and anxiety felt by some Facebook users, whether it’s through feelings of exclusion, pressure to be entertaining, paranoia or envy of others’ lifestyles," says Charles.
"Like gambling, Facebook keeps users in a neurotic limbo, not knowing whether they should hang on in there just in case they miss out on something good."