The extract doing the rounds seems to have been first posted on Reddit, so I have no great expectation for its validity. But to take it at face value, here is the full text:
The February 2008 form requests that Mr. Spears would be appointed as Britney's conservator in "orders related to dementia placement or treatment in the Attachment Requesting Special Orders Regarding Dementia (form GC-313 under Probate Code section 2356.5 be granted."
Underneath the header "DEMENTIA POWERS," the aforementioned "Probate Code Section 2356.5 allows conservators to request particularly strong powers if the conservative allegedly suffers from dementia. If the conservatee has a dementia-related illness, the conservator may be empowered to place the conservatee in a locked-door institution and to authorize the administration of medications 'appropriate to the care of dementia.'"
It simply notes that Mr Spears has requested conservatorship on the basis of dementia. And then lists powers that would grant him.
It gives no clue as to what may have caused the dementia.
But dementia is not a mental illness. Symptoms - include confusion, memory loss, impaired judgement, personality changes. It can be temporary, permanent, degenerative. It can be caused by brain damage, drug side effects, drug interaction, dehydration and degenerative diseases such as Alzheimer’s.