Some other people get mugged and stuffed into the box. Once inside, they can easily forget how they got there. They frequently blame themselves, even when it's obvious to everyone on the outside that it was the muggers' fault. It's a personal hell decorated with memories.
The boxes are about the same for both groups. Once a person has spent enough time isolated in the dark box, their eyes adjust. Not completely, just enough to read the sign over the most visible exit. It says "Death."
I just happened upon a blog post prompted by an attempt to ban the book SPEAK from public school libraries. It was about rape. It was courageous and moving and made a compelling argument for keeping books like SPEAK available. Because some teens need to know they're not alone. Because it sure feels that way when you're in a box.
It made me think. "My characters have nothing like that, no horrible past for readers to latch onto. Maybe I wasn't hard enough on them. Not edgy enough."
Then I thought again. "No. They don't have a horrible past because that wasn't my experience. Other people can tell their stories. I tell my stories."
I knew that already. I mean, DRIVERS is already written. I've already solved the problem of how to make getting locked quietly into a box interesting. Depression is hell, regardless of how one got there. I simply put a face on that hell, so my readers will know they're not alone—and it's not their fault.
I've never seen a book that did that. Not for people in the first group.