DEMENTED
brainsick, crazy, demented, disturbed, mad, sick, unbalanced, unhinged
(adjective) affected with madness or insanity; “a man who had gone mad”
Source: WordNet® 3.1
Etymology
Adjective
demented (comparative more demented, superlative most demented)
Insane or mentally ill.
Suffering from dementia.
(informal) Crazy; ridiculous.
Verb
demented
simple past tense and past participle of dement
Source: Wiktionary
De*ment"ed, a. Etym: [From Dement.]
Definition: Insane; mad; of unsound mind.
– De*ment"ed*ness, n.
DEMENT
De*ment", v. t. Etym: [L. dementare, fr. demens, -mentis, out of
one's mind, mad; de + mens mind. See Mental, and cf. Dementate.]
Definition: To deprive of reason; to make mad. [R.] Bale.
De*ment", a. Etym: [L. demens, -mentis.]
Definition: Demented; dementate. [R.] J. H. Newman.
Source: Webster’s Unabridged Dictionary 1913 Edition