Peter's Facebook friends knew something was wrong months before he had a manic episode. He had been posting about expensive shopping trips and name-dropping celebrities he claimed to have partied with—seemingly out of character for the 26-year-old former dental student from Atlanta. When Peter (not his real name) ran away from home in April 2013, he unleashed a flurry of paranoid, all-caps status updates saying his family was out to get him. Meanwhile his sisters left messages on his Facebook wall begging him to come home.

What might have been a family affair a decade ago instead played out in front of hundreds of eyes, as friends and acquaintances watched the saga unfold on their news feeds. Some people sent him private messages. Others posted on his wall. Many commenters expressed support and concern, but a few were mocking and unhelpful. One person wrote “lol.” Most people, however, only watched.

Mental health crises such as Peter's are being captured on social media with increasing regularity. Posts on Twitter by actors Charlie Sheen and Amanda Bynes, for example, chronicled their psychological unraveling before millions of followers, sparking intense debate among celebrity watchers about the appropriate reaction to their attention-grabbing tweets.

People who witness such events among their own friends face a challenging question: Should they respond—and if so, how? “Mental illness is not like the flu,” says computational social scientist Munmun De Choudhury of the Georgia Institute of Technology. Unlike other conditions, “people are often not comfortable discussing these things.” The deep-rooted stigma of the topic discourages people from probing the emotional states of others. Yet silence compounds the problem because struggling individuals can come to believe they are suffering alone and avoid seeking help for fear of ridicule.

Social media could radically change this attitude. As people increasingly share very private experiences online, observers are gaining unparalleled insight into one another's mental lives. Digital interactions—through blog posts, social media updates, Instagram photos, and more—produce a wealth of data about a person's emotions and behaviors. Close family members and distant acquaintances alike can glimpse disturbing patterns in these outlets and offer simple forms of support. By breaking the silence, they can ease a colleague's or companion's pain—and they can chip away at the stigma that keeps many from seeking help in the first place.

Emotional Voyeurs

Social media might not seem like a panacea for mental illness at the outset. People often err on the side of silence when a typically private sentiment is expressed in a public manner. In a 2013 study, for example, Megan A. Moreno, an adolescent medicine specialist now at the University of Washington, and her colleagues asked college students whether they had ever seen a Facebook status update from a friend mentioning depression or anxiety. A majority said they had, but when the researchers asked students if they would respond to such a post, they were unsure. Most said they would if the post were written by a close friend or relative but not by a more distant acquaintance. In the latter case, they would expect someone closer to the person in distress to do the heavy lifting.

The students' aloofness may be partly explained by the bystander effect—a psychological phenomenon first proposed in the 1960s, in which people become less likely to intervene in a crisis as the number of witnesses grows. A similar diffusion of responsibility occurs online. In multiple studies, researchers have posed as people requesting help by e-mail and in chat rooms. The findings have been consistent: the bigger the online community, the less likely a recipient is to respond. On platforms such as Facebook and Twitter, where no one knows who has seen what, a sense of personal responsibility may be particularly elusive.

People might also hesitate because they cannot gauge whether a situation is serious, suggests psychologist Jill Berger of the University of Maryland, who has surveyed college students' responses to online signs of suicidal thinking. Although they are concerned, she says, they do not want to “make a big deal” about something potentially mundane and risk an awkward interaction.

Even if a situation is not yet dire, Berger counsels that it warrants follow-up. Social media acquaintances may be critically positioned to offer support. Writing a status update or tweeting about a problem can be easier than talking about it face-to-face, particularly for stigmatized issues such as mental illness. Evidence suggests that people feel less inhibited online. Furthermore, adolescents and young adults, who are at an age when mental disorders typically manifest, are more inclined to disclose sensitive information to peers than to adults.

Moreno believes that these posts are an important outlet for vulnerable individuals. Often, she says, posters are looking for emotional support and encouragement. On Facebook, “you don't have to wait in line for a therapy appointment—you can get that positive feedback within seconds.” According to Moreno, posting frequently about mental health problems on social media could indicate that a person is not getting the help he or she needs offline. To a person in crisis, not getting a response may be “almost worse than getting a negative response,” she adds, because it seems like “nobody is listening and nobody cares.”

Unlocking Support

The work of scientists studying the reticence of onlookers makes it clear that people do hear online cries for help—they just do not know how to reply. The good news is that people can be encouraged to take action. The bystander effect, for example, now appears to be more nuanced than was initially thought. Recent studies have found it to be less powerful than in early experiments, perhaps because people are more aware of it today.

And there may be ways to reduce or even reverse the effects. In a 2011 update on the bystander effect, Peter Fischer, a psychologist now at the University of Regensburg in Germany, and his colleagues analyzed data from all previous studies of the phenomenon and found that it diminishes significantly as the situation becomes more obviously dangerous. When faced with a sure emergency, the self-doubt that holds people back often disappears.

The key to unlocking support is therefore educating people about how serious mental health crises can be, how to spot one and what witnesses can do to help. Mental health “first aid” programs, for example, can teach people how to recognize and respond to a mental health emergency in real life. Certain groups, such as college resident advisers (RAs), traditionally tasked with identifying distressed students, are learning to notice warning signs on social media as well. Moreno thinks that RAs and other youth leaders, such as team captains and church group organizers, are well positioned to detect crises unfolding online and either reach out themselves or pass the information along to a more qualified individual, such as a school counselor.

Meanwhile Facebook is encouraging its users to act when they see troubling posts. In 2011 the company added a tool to anonymously report suicidal content. Once you submit a report, Facebook informs the person in distress that a contact has expressed concern and offers links to emergency hotlines and the opportunity to chat with a crisis worker.

Recipients are, of course, free to decline, but research indicates that most people who post about their troubles do want help. In one of several recent studies, Moreno and her colleagues asked 60 college freshmen how they would like to be treated by someone who saw signs of their depression on Facebook. Almost every student said that they would be open to communication from friends, professors and RAs. More than 30 percent said they would be okay with receiving a message from a stranger.

Most respondents, however, added that they preferred people to contact them directly—either one-on-one, over the phone or via e-mail—and with an open mind. “The emphasis was on this idea of being inquisitive: asking questions rather than making judgments,” Moreno says.

In addition, some amount of automated support could help sufferers. Researchers at Harvard University, Dartmouth College and other institutions are now developing apps that monitor smartphone and social media activity to detect signs of distress. This data trail could allow clinicians to intervene before symptoms intensify or send users automated suggestions for how to improve their mood or get back in touch with reality.

Learning to Listen

Beyond offering new lifelines for people under duress, social media may now be lifting the veil of silence that has long shrouded mental disorders. Social scientists have found that throughout history, prejudice is best dismantled when people interact frequently with others unlike themselves. Indeed, a 2012 meta-analysis of approaches to reducing stigma concluded that simply having contact with people with mental health conditions trumps social activism and education in getting adults to abandon their preconceptions.

Social media onlookers might even experience a boost in empathy and feel more willing to reach out after discovering a friend's struggles online. In a 2014 study led by health communication expert Nichole Egbert of Kent State University, students were also significantly more likely to support a depressed friend if they identified with his or her problem.

Along those lines, the New York City branch of the National Alliance on Mental Illness launched a social media campaign called “I Will Listen” in October 2013. In a series of videos and Facebook posts, actress Mariel Hemingway, writer Andrew Solomon and other public figures pledged to listen to those with mental illness “with an open mind and without judgment” and shared personal stories on these issues. Since the start of the campaign, dozens of people have followed suit, documenting their own experiences with mental illness on Twitter, Vimeo and Instagram with the hashtag #IWillListen.

As Moreno sees it, social media “offers us tools that we didn't have 10 years ago,” when the same people were walking around with little social support and few opportunities for others to witness their distress. Now that we have the tools, it is just a matter of using them.