demented vs brainsick

demented and brainsick both are adjectives.

Word	Noun	Adjective	Verb	Adverb
demented	No	Yes	No	No
brainsick	No	Yes	No	No

As adjectives, demented and brainsick are synonyms defined as:

Other synonyms of demented include crazy, disturbed, mad, sick, unbalanced, unhinged.

demented (adjective)	brainsick (adjective)
affected with madness or insanity	affected with madness or insanity