Well, I can just share our experience. DD started something like this when she was 12. It happened kind of gradually and we are still going through it a bit at 13.5. She just seemed to lose motivation for nearly everything. And she seemed unhappy a lot. I did come to understand it as related to adolescence. I remember reading something on adolescence somewhere and the author said something to the effect that this is a time when you stop caring about the things you used to care about. And i thought...yes! Some kids have a single strong interest like dance or a sport or something that they can ride right through the transition. But most don't. It is the loss of childhood. You used to care about Ninjago, or the Harry Potter or going fishing with your dad or having manicures with mom. And then those things just don't matter any more. It really is a huge loss and terribly sad, but you may not even know what you are sad about. And no one around you says "you are going through your first major life transition during which you will lose most of who you have been, and this should be consciously grieved and mourned."