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"Till Facebook does us part." People who spend hours every day on the social networking site are more likely to get divorced than those who don't use it, finds a new study in Computers in Human Behavior.

It could be that people in crappy relationships are just more likely to spend time avoiding their spouses by posting statuses and liking photos, says study coauthor Sebastian Valenzuela, Ph.D., of the Pontifical Catholic University of Chile. On the other hand, Facebook exposes you to old flings and new mates, makes sneaking around on your wife easier to hide, and also leads to addictive behaviors--all of which won't do your marriage any favors, Valenzuela adds. (Heading for the altar? You might be surprised at these 5 Signs Your Marriage Will Last.)

Like the old "guns don't kill people . . . people kill people" line, you can't blame all your problems on Mark Zuckerberg. But a broken marriage isn't the only bad thing researchers have linked to Facebook use.

It saps your motivation to give back. "Liking" or showing support for charity organizations on Facebook lowers the odds that you'll donate your time or money to those causes, finds research from the University of British Columbia. Your public thumbs-up satisfies your desire to look charitable in front of others and makes you feel good about yourself, which wipes out your motivation to volunteer time or cash, the researchers say.

It crushes your mood. The more time you spend on Facebook, the more your attitude sours, shows a study from Austria. You probably realize that staring at profiles and pictures isn't a very productive use of your time. And the recognition that you've wasted a big chunk of your day on something meaningless clouds your mood, the researchers explain. (Excessive smartphone use can have a negative impact on your life. Here are five reasons you might want to power down.)

It makes you dumb. After looking at their own Facebook pages for 5 minutes, people took 15 percent longer to answer simple math questions. That's because your profile inflates your ego, which undercuts your brain's motivation to perform, say the researchers from the University of Wisconsin-Madison.

It renders your life unsatisfying. The more you surf, the less satisfied you feel about life in general, indicates a study from the University of Michigan. It's inevitable that some of your friends will be posting about the fun, interesting stuff they're doing. And contrasting your own boring life to theirs--something Facebook basically forces you to do--could explain these negative consequences, the authors say.

It leaves you lonely. Scanning your friends' profiles increases feelings of social exclusion and "invisibility," finds research from Australia. Because you're observing your buddies but not interacting with them, you feel cut off or left out, the study suggests. (The good news: If you actively post things--pics, updates--and your pals respond to your posts, these bad feelings go away, the study shows.)