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It was Christopher’s therapist who suggested he look for help online. His wife had cheated on him, and he had been struggling since their divorce, but the $25 copays were adding up. His therapist proposed an online support group—free, discreet, available 24/7.

So he went, naturally, to Facebook, where a search turned up multiple private groups for people dealing with a partner’s infidelity. (Christopher had divorced his wife after finding out that their daughter was not his biological child. When I interviewed him, he asked that we withhold his real name.) From there, he got invitations to other support groups on Facebook, more targeted and even more specific: a group for families dealing with misattributed paternity, a group for children learning the same from DNA tests.

The support groups Christopher stumbled into are just a tiny corner of the vast ecosystem of private Facebook groups. Over the past year, the company has been consciously emphasizing groups—part of an effort, per Mark Zuckerberg, to “give people the power to build community and bring the world closer together.” These groups cover interests ranging as widely as the human imagination. Many are “closed,” which in Facebook terminology means they are findable, but only members can see their content. Some are “secret” and unsearchable, and membership is by invitation only.

It’s not surprising, then, that Facebook has turned into a gathering place for strangers sharing their deepest secrets. Emotional-support groups have sprung up around topics broad and narrow: diabetes, addiction, egg donation, a specific birth-control device now pulled from the U.S. market, parenting children who might grow up to be psychopaths, rare diseases that affect only a few dozen patients in the whole world. The internet has always promised to connect people by common interest rather than geography, and with its 2-billion-user base, Facebook is where those connections are often being made. “For people searching for support, [Facebook] is a one-stop shop,” says Andrea Downing, a moderator for BRCA Sisterhood, a support group for women who have tested positive for breast-cancer mutations.

Downing carries a mutation for BRCA1, which can raise the risk of breast cancer to more than 70 percent. Finding that out was devastating. “I did not know anybody who was going through the same experience,” she says. “When you can’t even talk to your own friends and family about what you’re going through, just living with that is really hard.” She eventually found out about BRCA Sisterhood on Facebook, where she suddenly found a few hundred women who understood exactly what she was going through. The women, she says, were a “lifeline.” They divulged their anxieties. They shared the latest research. They posted photos of their preventive mastectomies. BRCA Sisterhood has now grown to 10,000 members.

NGLY1 Families, on the other hand, has fewer than 60 members on Facebook, and it doesn’t expect to get much bigger. That’s because NGLY1 deficiency is extremely rare, known to affect only a few dozen patients. With those few dozen scattered around the world, Facebook is a vital node for connection. “This is pretty standard now. You would be hard-pressed to find a rare disease without a group,” says Matt Might, whose 10-year-old son has NGLY1 deficiency. Might is a member of multiple Facebook groups for NGLY1 and related diseases, where members support one another through health crises and share hard-won medical information about the rare disease. Recently, a member posted about a medical emergency, and Might told me he was able to direct the person to the right doctors.

Since Facebook has pivoted to groups, it has added several tools for group admins, including ways to filter membership requests and delete content from banned members. Most important, perhaps, it made the membership of closed groups private. Until earlier this year, nonmembers could see who had joined a group even if they could not see the posts inside. (Secret groups are unsearchable, and their membership lists have always been private.)

This had created obvious problems for support groups, which want to be findable but don’t want to broadcast their members’ private lives. Last year, Catherine St Clair decided to start a support group for people whose DNA tests revealed unexpected biological parents, after meeting another woman in the same situation on Facebook. St Clair created a closed group because she wanted other people to find it. And, of course, she invited the other woman. This was before Facebook made the change, and her membership quickly became public. “When she realized that, she dropped out real fast,” says St Clair.

So St Clair came up with an elaborate work-around: She made the actual group, DNA NPE Friends, secret and unsearchable, but then created a closed DNA NPE Gateway group. Anyone who wanted to join had to first request membership in the gateway before they were invited to the actual group. “Our members are so terrified, genuinely terrified, of being outed,” she explains. When I spoke to members of her group, more than one mentioned the fear that a father might kill someone upon finding out that his child was the product of an affair.

Back in March, Downing of the BRCA Sisterhood group found a Chrome extension that allowed marketers to scrape the membership lists of closed groups. She worked with a security researcher to submit the information to Facebook, which sent a cease-and-desist letter to the Chrome extension. On June 29, Downing noticed that Facebook had started restricting the membership lists of closed groups to members only. It’s unclear exactly when the change was made. A Facebook spokesperson declined to confirm a date but said the company had already been considering the change, based on feedback from other groups.

In July, Wired reported on a Facebook group for sexual-assault survivors that had amassed thousands of members. One day, administrators suddenly changed it into a group for sharing erotica, and trolls began harassing the members. It’s unclear whether the group was hacked or its creators had planned this from the start.

These events made Downing worry about other scenarios that could expose the members of BRCA Sisterhood. She considered taking the support group off Facebook entirely. But with nearly 10 years’ worth of posts on the site, the group couldn’t just pick up and leave. “It’s the only place that these groups can go,” she says of Facebook. Might echoed those concerns: “The problem is Facebook groups are not the best way. It’s the only way.” NGLY1 also has an active email list, he says, “but I know if we’re not on Facebook, we’ll miss people.”

Other moderators have noticed how Facebook’s algorithm shapes the discussion in groups. Posts in a group, not unlike the newsfeed, are sorted algorithmically by default. “If you click on the group, it tends to be the most popular content, but it’s not the most relevant,” says Dana Lewis, a member of several diabetes groups. For example, according to Lewis, the algorithm might keep showing a post whose question has been answered. And it might deprioritize posts from new members that don’t get much engagement—ensuring they get even less engagement in a form of algorithmic ghosting. It’s not exactly a friendly welcome to a support group. “I don’t think Facebook has done a good enough job,” says Lewis. “They have a lot of room to improve.” A Facebook spokesperson noted that members can choose to see most-recent posts first, and admins see posts in their approval queue in reverse chronological order.

Anyone can start a Facebook group—including people trying to profit off one. While many founders of support groups are people simply trying to find others like themselves, some have used the groups as extensions of their business. In November 2017, The Verge investigated a prominent group called Affected by Addiction, whose founder was even invited to speak at Facebook’s first Communities Summit earlier that year. The founder, it turns out, was also a marketer for treatment centers that mined the group for potential patients, according to The Verge. The ties had not been disclosed.

Other groups are more up front about selling services. For example, the Infidelity Support Group—20,000 members strong—is run by Bob Huizenga, whose pinned post urges users to sign up for his “FREE Introductory Level of the Infidelity Recovery Center” before pushing additional services that cost as much as $915.

For patient-led groups, money is also a tense topic. Some have entirely banned fund-raising, even for a good cause. “Once it happens, everybody jumps on the bandwagon,” says Downing of BRCA Sisterhood. “We have purposely and carefully kept it out of the group.” Facebook support groups, after all, are full of emotionally vulnerable people trusting strangers on the internet. It’s the kind of access scammers dream of.

Facebook does not allow advertisers to directly target a group (though marketers have proposed work-arounds). A spokesperson also reiterated to The Atlantic a policy in August about predatory ads, which prohibited ads for bail bonds and restricted ads for rehab centers to those certified by a third party.

When Facebook announced its decision to emphasize groups in 2017, the company also changed its mission statement. “It’s not enough to simply connect the world; we must also work to bring the world closer together,” Zuckerberg wrote. The change came after its attempt to connect the world ended up spreading fake news with sometimes disastrous consequences. Facebook had failed to understand the machine it built. With its new mission, it is tweaking that machine: Coding algorithms and writing policies will affect millions of people who have come to depend on Facebook as a very real support network.

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