Demented means out of one's wits, or robbed of memory and reason by an ageing brain. Demented with grief, a demented shriek, care for the demented.
The medical use is now avoided, since living with dementia is the term families and clinicians prefer and demented has become an insult. The loose sense, meaning wild with some feeling, is the commoner one in speech.
1adjectivedementedOut of one's wits with rage or grief, or robbed of memory and reason by an ageing brain.
“When the children went missing, their mother was almost demented with worry.”
demented is a state.
Latin dementare means to drive out of one's mind, from de plus mens, the mind.
Proto-Indo-European
*men- (think)
Latin
demento
English, today
demented
From dement + -ed. Past participle of dement + -ed, from Latin demento.
Etymology from Wiktionary, CC BY-SA