I think something happened right at the point of the justin split (maybe the media backlash and being sad about splitting from her first bf? We’ve all been there…), got worse during the kevin era (drink, drugs, rebelling against the “system”, tired of working and just wanted to be a normal girl her age for a bit) then ppd triggered a bigger breakdown. I have a close friend that suffered terribly after having her daughter 13 years ago and she really has not been the same since (bipolar, anxiety etc)
I think since around 2003 things were being heavily covered up and now she is not being managed/monitored its just on full display to us all.