I'm just guessing, as I don't recall any medical expert of Britney's coming forth with a diagnosis, but, I *think* she had something closer to postpartum psychosis, only without drowning her kids. Or that set off deeper issues, like being bipolar. She started acting more crazy than usual, almost right after her second child was born and she realized her then husband was only around for the gravy train of money & fame.
However, he did seem to straighten out and take custody of the kids. And we haven't heard anything bad on that front.
Then Britney's dad gained conservatorship over her and it took about 3(?) years for Britney come back as "normal."
Being that she's still under a conservatorship now, I suspect she was diagnosed with something, she just prefers to keep it private.
Since Amanda's stay in the hospital has been extended from 48 hours to 2 weeks, I would guess that she's in the same situation. Her parents are also going for the conservatorship I would guess she's in the same type of situation.