BKD, you might take a look at some of my very earliest posts on the forum, from when DD16 was the same age as your child.
She had always been intense and highly autonomous/stubborn-- but that year, things took off and snowballed in a way which was (and still is, in many respects) a complete and total mystery to me.
My DD later sustained a tremendous trauma that led to additional diagnoses (when we could finally get her cooperation to see a series of mental health professionals, that is)--
but we have had to come to terms with the fact that she probably has an anxiety disorder that is fairly severe and will likely be something she has to deal with all of her life.
What has made it better? Honestly-- more autonomy. For her, much of the root cause is about control. It's what is underneath even the socially-prescribed perfectionism. Tackle that, and the rest of it self-resolves.
I would say to you-- keep reading, keep digging, and bear in mind that you know your child better than ANY outsider ever can. When I read about socially prescribed perfectionism and related anxiety disorders, it was as though a neon sign flickered on, saying "Yes! This! This! This!" for the first time in my years of parenting this child, I felt like I'd been handed a key that unlocked insights into what made her tick.
NOTHING else had ever quite fit. If I hadn't seen that, hadn't had that moment, she would certainly have been misdiagnosed and probably medicated (inappropriately), which would NOT have helped her in the least-- actually, stimulant meds are bad, bad, BAD news for her, even caffeine at levels found in coffee is a definite no-no for her.
I also recommend Misdiagnoses,... (the book) because that, too, led to a lot of self-reflection on our part about why DD could appear to be depressed, have an ASD, have ADD, etc. etc. but just-- not-- quite.
Some people would say that we coddled DD through those years. I disagree. She could avoid school and still do very well. So we let her. I realize that not everyone has that option-- but letting her complete high school in an online setting, while far from ideal in many, many ways-- let her have the breathing room that she needed in order to build a framework of good habits, self-care that is meaningful, and time to explore within herself. She's PG. She has that time, obviously.
I won't say that I truly know what caused all of this. I don't. I don't even think that there was any one trigger for the latent potential which was probably always there in her. I do believe that it was a perfect storm of factors which occurred when she was 8-10yo.
VERY best wishes to you as you wrestle with this. There is very little out there in the way of good information about mental health struggles in high ability children and adolescents, I'm afraid.
