One of my DC had such a shit adolescence.
MH problems, depression, anxiety , CAMHS appointments, counselor, eating disorders, self harm. Fighting to keep them in school. Fighting to keep them from retreating to a world as small as their mattress.
I can remember so clearly a parents group running alongside a young patients anxiety group. Most parents were , to a greater or lesser extent, grateful that their offspring were responding to treatment, after a year or two. I fell apart. It had been four long hard painful destructive years for everyone in our family. I thought then that my DC was different, that it might be MH problems for life.
I can't really describe the difference now. I am just so grateful. DC finally crashed out of school. Decompressed for a year. Chivvied them into mundane part time jobs, so as to have a reason to get out of bed. Gradual improvement. Returned to education. Nail biting stress, but found their own way to cope. Success in Access course. Off to Uni in September. But, best of all, happy. Sense of humour returned. Good social life. Self belief.
Maybe will still crash and burn. Maybe not . But climbed out from under once, so can do so again.
Believing there's no possible positive future? I think that's part of depression. And yes, whilst " growing out of it" might sound a bit facile, once the hormonal and identity maelstrom of adolescence is past, the waters do become more navigable and maneagable for some.
All best wishes for a better future.