But there are several circumstances where people actually feel better after using Facebook.
According to Toma, if users focus on their own profile instead of their friends' profiles sometimes they feel better than they did before they logged on.
"Because of selective self-presentation, we put our best foot forward, or face-forward in the case of Facebook, so by looking at our own profile more, we feel good about ourselves," she said.
Moira Burke, a doctoral candidate in Human-Computer Interaction at Carnegie Mellon University says there is no evidence that social networking sites cause unhappiness in and of themselves. She surveyed 415 Facebook users in July 2009 and again eight months later. Participants were asked to fill out a questionnaire surveying loneliness, among other factors. In March 2010, the users were surveyed again. Survey responses were then matched with participants' Facebook activity during the eight month period.
By surveying users on how lonely they felt at a single moment in time and comparing their answers to their online activity, Burke found a correlation between passive consumption, like looking at friends' pictures, and loneliness.
"At a single point in time, you can't tell if clicking on feed stories causes loneliness or lonelier people tend to click on more stories. But when we survey people multiple times, we find that the correlation goes away – loneliness isn't affected by consumption," Burke said.
In the study Burke also found engaging with people one-on-one in Facebook can help people feel less lonely.
"We found that overall, the more engaged people are in Facebook, the better they feel," she said.
Burke will discuss her study results at the Conference on Human Factors in Computing Systems in April.
In the end, the way we feel when on Facebook (or any other social networking site) most likely depends on our personality traits. In other words, the way we typically view the world also colors the way we perceive ourselves and others on Facebook. It's a concept supported by Burke's research.
"Individual differences in social skills and self-esteem influence how people use social media and the effects those media have on them," Burke explained.
Not surprisingly, in Burke's study, those with lower communication skills are less likely to interact one-on-one, but they feel more of a connection when they do interact on Facebook.
And people with great social skills who are passively consuming other people's news feeds may feel little effect, but for those who find it hard to communicate in person, the news feeds can be beneficial. Those with high self-esteem tend to have more friends.
Kris Ortiz, 22, a Hofstra graduate student studying speech communication, says he feels great after using Facebook.
"Seeing wall posts and messages and 'likes' makes my mood a lot better," she said. "We all want to be remembered and thought about; it's like getting a card on your birthday."
Steven Panzarella, a junior at Hofstra, logs on to Facebook to maintain relationships with friends around the world.
"When I get on Facebook, I'm happy; I'm keeping up with friends and getting a chance to see what they're doing. When I log off, I feel content," he said.
According to Facebook.com there are more than 500 million users and more than 50 percent of the users log into Facebook at least once a day.