Kaia Gerber and Gigi Hadid, two of the world’s most in-demand models, get hundreds of thousands of likes on nearly every photo they post to Instagram. Occasionally, their selfies also come with a warning: “Social media seriously harms your mental health.”

The phrase, printed on the back of a transparent cellphone case, appears once in a while, usually in their mirror selfies or when they’re photographed holding their phone. They’re not alone: multiple models and influencers have been photographed with the case, including Madison Beer, Hailey Bieber, Delilah Belle, and dozens of other Instagram users who tag themselves with the case every month.

Multiple studies have found that prolonged social media use is linked to depression and loneliness, and easing the pressures that come with constant connectivity has been a focus of large tech companies in recent years. This case’s popularity suggests it’s not just typical users who feel the platforms’ effects: the world’s most beautiful people who have millions of followers and whose careers depend on Instagram amplifying their looks also worry about the effect social media has on their brains and self-esteem.

“It’s just a constant reminder on my stories that we just do it for the likes,” says Petra Vukotic, an Italian model with nearly 25,000 followers who sometimes poses with the case. “I look at it as a reminder for me that the likes and social media are a drug. It’s addictive. It’s a form of validation that we are worthwhile.”

The mental health warning phone case comes from Urban Sophistication, a four-year-old brand that specializes in clothes and accessories featuring self-referential, ironic branding and phrases. The team released the $35 case in December 2017, and it remains a best-seller that’s turned into a signifier for models, wannabe influencers, and Instagram users who post on social media regularly.

“We can’t say we expected that, but that was the best scenario we had in mind,” says Elad Yam, 23, who owns Urban Sophistication with his sister Neta, 21.

The irony of sharing its message through the very medium it’s warning against is intentional, and the case likely resonates with Instagram’s power users because it physically manifests the complicated relationship they have with the app. One of Instagram’s biggest hurdles, possibly the most important one currently, is building an uplifting space that doesn’t drive its most successful users into spirals of despair.

Christina D’Alessandro, who has nearly 8,500 followers, says the case communicates how she feels about her relationship to Instagram. “Even though I would get all of these compliments … at the end of the day I felt alone,” she says over Instagram DM.

People noticed her scoliosis in photos, D’Alessandro says, which made her self-conscious. “When I got my confidence back was around the same time I discovered this case, and I wanted people to know that whether good or bad, social media will affect you!”

Neta and Elad said they felt a tension between creating for Instagram while also remaining thoughtful about their products and messages. Neta says she deletes the app from her phone occasionally, even just for hours at a time. “I guess that inspires the idea because it’s just how we feel,” she says. “But also, you can’t be without [Instagram], so it’s very mixed feelings.”

They’re tied to Instagram whether they like it or not. To their benefit, Neta and Elad know how to capitalize on it. The duo wanted their mental health message to reach as many people as possible, so they settled on a case because people carry their phones with them all the time. That means the case shows up in photos routinely, unlike a shirt someone wears only once in a while. A phone case is primed to go viral.

“What’s a better place to have this warning than on social media, on our Instagram?” Elad asks. “So when you scroll through your feed every now and then, you see this warning.”

The siblings started out making T-shirts and got their break when they met Kardashian family pal Jonathan Cheban on a flight. (He was later photographed wearing their work, as well as Kylie Jenner, Kendall Jenner, and Kourtney Kardashian.) But their products most resonated on Instagram once they introduced their phone cases. The mental health case, in particular, took on a life of its own. Elad says most people come across the case in a photo and then seek it out for themselves, although celebrity stylists sometimes reach out for their clients, too.

Starting their business four years ago meant taking advantage of the tools Instagram provided them. The siblings tagged people, hoping they’d see their products, and messaged influencers looking for a response. “At some point, you see that some celebrities do read their DMs,” Neta says. “We saw Instagram makes the world so small. You understand that everything is accessible.”

Plus, Instagram’s algorithm seized on the viral nature of the case and distributed it on Explore pages and at the top of people’s feeds. The models who posed with it propelled it even further.

But as their brand grew, Neta and Elad faced the same pressures as influencers to keep producing relatable content. “You get in this realm of content, content, content, when it’s supposed to be about what that content is about,” Elad says.

The women I spoke to about their cases all say the same thing: they use Instagram, they’re good at it, and it gives them a platform — but it also makes them feel bad.

Maria Gabriela Santos, who has around 7,700 followers, says it’s easy to forget that social media presents the way we want to be seen online, and not who we really are. “I hope that everyone realizes how social media changes our minds and the way we see each other,” she says over Instagram DM. “Our social media appearance is not our real personality.”

“The irony is that we all know that ‘consuming’ too much social media is bad for our mental health, and we still do it,” she says. “Like smoking, you get addicted!”

Instagram has acknowledged that its app can encourage negative behavior and thinking, and it’s started experimenting with ways to remedy the issue. The company began testing a feature earlier this year that hides the like count on posts, so people can “focus on the photos and videos.” It also implemented multiple features to address online bullies. Apple and Google have designed time management tools so people can limit their app usage, and all of these changes happened over only the past two years.

Instagram launched Elad and Neta’s business and empowered them to sell their cases. It gave their phone case buyers a platform to share their photos and grow their own brands. All that reach and desire to engage an audience of millions doesn’t come without trade-offs, however. When you entangle your life in an app that makes you feel bad, the only option other than quitting is to stick it to the platform with a phone case that says it all.