Having a case of the Mondays every day of the week? Well, don't sign in now, but Facebook might be the problem.

According to a new study from the University of Michigan, users' levels of sadness increased the longer they used Facebook. The university conducted a study where they monitored a group of 82 college-aged Facebook users. The group answered questionnaires five times a day for two weeks, and rated their well-being at the start and end. After the 14 days were up, the users began to feel worse about themselves. The more they browsed the site, the more their "moment-to-moment" mood worsened. Even if they had a huge network of friends, or a small one, the results were the same. 

"We were able to show on a moment-to-moment basis throughout the day how people’s mood fluctuated depending on their Facebook usage,” said social psychologist Ethan Kross, lead author of the University of Michigan study.

"We measured lots and lots of other personality and behavioral dimensions, like, for example, frequency of Facebook use," he said. "But none of the factors that we assessed influenced the results. The more you used Facebook, the more your mood dropped."

“Loneliness predicted Facebook use, and loneliness also predicted how bad people felt," Kross continued. "But the effect of Facebook on how people felt was independent of loneliness.”

Kross says that the researchers don't know what aspect of the social network is contributing to these results. 

“One of the things we don’t know is what aspect of Facebook use is contributing to these results,” Kross said. “We’re really just beginning to scratch the surface as to how exactly these interactions work and how they influence us.”

One thing is for certain: it's not going to hurt to turn off your gadgets and get some sunshine.

[via LA Times]