No one joins Facebook to be sad and lonely. But a new study from the University of Michigan psychologist Ethan Kross argues that that’s exactly how it makes us feel. Over two weeks, Kross and his colleagues sent text messages to eighty-two Ann Arbor residents five times per day. The researchers wanted to know a few things: how their subjects felt overall, how worried and lonely they were, how much they had used Facebook, and how often they had had direct interaction with others since the previous text message. Kross found that the more people used Facebook in the time between the two texts, the less happy they felt—and the more their overall satisfaction declined from the beginning of the study until its end. The data, he argues, shows that Facebook was making them unhappy.

Research into the alienating nature of the Internet—and Facebook in particular—supports Kross’s conclusion. In 1998, Robert Kraut, a researcher at Carnegie Mellon University, found that the more people used the Web, the lonelier and more depressed they felt. After people went online for the first time, their sense of happiness and social connectedness dropped, over one to two years, as a function of how often they used the Internet.

Lonelier people weren’t inherently more likely to go online, either; a recent review of some seventy-five studies concluded that “users of Facebook do not differ in most personality traits from nonusers of Facebook.” (Nathan Heller wrote about loneliness in the magazine last year.) But, somehow, the Internet seemed to make them feel more alienated. A 2010 analysis of forty studies also confirmed the trend: Internet use had a small, significant detrimental effect on overall well-being. One experiment concluded that Facebook could even cause problems in relationships, by increasing feelings of jealousy.

Another group of researchers has suggested that envy, too, increases with Facebook use: the more time people spent browsing the site, as opposed to actively creating content and engaging with it, the more envious they felt. The effect, suggested Hanna Krasnova and her colleagues, was a result of the well-known social-psychology phenomenon of social comparison. It was further exacerbated by a general similarity of people’s social networks to themselves: because the point of comparison is like-minded peers, learning about the achievements of others hits even harder. The psychologist Beth Anderson and her colleagues argue, in a recent review of Facebook’s effects, that using the network can quickly become addictive, which comes with a nagging sense of negativity that can lead to resentment of the network for some of the same reasons we joined it to begin with. We want to learn about other people and have others learn about us—but through that very learning process we may start to resent both others’ lives and the image of ourselves that we feel we need to continuously maintain. “It may be that the same thing people find attractive is what they ultimately find repelling,” said the psychologist Samuel Gosling, whose research focusses on social-media use and the motivations behind social networking and sharing.

But, as with most findings on Facebook, the opposite argument is equally prominent. In 2009, Sebastián Valenzuela and his colleagues came to the opposite conclusion of Kross: that using Facebook makes us happier. They also found that it increases social trust and engagement—and even encourages political participation. Valenzuela’s findings fit neatly with what social psychologists have long known about sociality: as Matthew Lieberman argues in his book “Social: Why Our Brains are Wired to Connect,” social networks are a way to share, and the experience of successful sharing comes with a psychological and physiological rush that is often self-reinforcing. The prevalence of social media has, as a result, fundamentally changed the way we read and watch: we think about how we’ll share something, and whom we’ll share it with, as we consume it. The mere thought of successful sharing activates our reward-processing centers, even before we’ve actually shared a single thing.

Virtual social connection can even provide a buffer against stress and pain: in a 2009 study, Lieberman and his colleagues demonstrated that a painful stimulus hurt less when a woman either held her boyfriend’s hand or looked at his picture; the pain-dulling effects of the picture were, in fact, twice as powerful as physical contact. Somehow, the element of distance and forced imagination—a mental representation in lieu of the real thing, something that the psychologists Wendi Gardner and Cindy Pickett call “social snacking”—had an anesthetic effectâ one we might expect to carry through to an entire network of pictures of friends.

The key to understanding why reputable studies are so starkly divided on the question of what Facebook does to our emotional state may be in simply looking at what people actually do when they’re on Facebook. “What makes it complicated is that Facebook is for lots of different things—and different people use it for different subsets of those things. Not only that, but they are also changing things, because of people themselves changing,” said Gosling. A 2010 study from Carnegie Mellon found that, when people engaged in direct interaction with others—that is, posting on walls, messaging, or “liking” something—their feelings of bonding and general social capital increased, while their sense of loneliness decreased. But when participants simply consumed a lot of content passively, Facebook had the opposite effect, lowering their feelings of connection and increasing their sense of loneliness.

In an unrelated experiment from the University of Missouri, a group of psychologists found a physical manifestation of these same effects. As study participants interacted with the site, four electrodes attached to the areas just above their eyebrows and just below their eyes recorded their facial expressions in a procedure known as facial electromyography. When the subjects were actively engaged with Facebook, their physiological response measured a significant uptick in happiness. When they were passively browsing, however, the positive effect disappeared.

This aligns with research conducted earlier this year by John Eastwood and his colleagues at York University in a meta-analysis of boredom. What causes us to feel bored and, as a result, unhappy? Attention. When our attention is actively engaged, we aren’t bored; when we fail to engage, boredom sets in. As Eastwood’s work, along with recent research on media multitasking, have illustrated, the greater the number of things we have pulling at our attention, the less we are able to meaningfully engage, and the more discontented we become.

In other words, the world of constant connectivity and media, as embodied by Facebook, is the social network’s worst enemy: in every study that distinguished the two types of Facebook experiences—active versus passive—people spent, on average, far more time passively scrolling through newsfeeds than they did actively engaging with content. This may be why general studies of overall Facebook use, like Kross’s of Ann Arbor residents, so often show deleterious effects on our emotional state. Demands on our attention lead us to use Facebook more passively than actively, and passive experiences, no matter the medium, translate to feelings of disconnection and boredom.

In ongoing research, the psychologist Timothy Wilson has learned, as he put it to me, that college students start going “crazy” after just a few minutes in a room without their phones or a computer. “One would think we could spend the time mentally entertaining ourselves,” he said. “But we can’t. We’ve forgotten how.” Whenever we have downtime, the Internet is an enticing, quick solution that immediately fills the gap. We get bored, look at Facebook or Twitter, and become more bored. Getting rid of Facebook wouldn’t change the fact that our attention is, more and more frequently, forgetting the path to proper, fulfilling engagement. And in that sense, Facebook isn’t the problem. It’s the symptom.

Maria Konnikova is the author of the New York Times best-seller “Mastermind: How to Think Like Sherlock Holmes.” She has a Ph.D. in psychology from Columbia University._

Photograph by Luong Thai Linh/EPA/Corbis