mental rejection vs disbelief

mental rejection and disbelief both are nouns.

Word	Noun	Adjective	Verb	Adverb
mental rejection	Yes	No	No	No
disbelief	Yes	No	No	No

As nouns, mental rejection and disbelief are synonyms defined as:

Other synonyms of mental rejection include incredulity, scepticism, skepticism.

mental rejection (noun)	disbelief (noun)
doubt about the truth of something	doubt about the truth of something
	a rejection of belief