cognitive state vs mental state

cognitive state and mental state both are nouns.

Word	Noun	Adjective	Verb	Adverb
cognitive state	Yes	No	No	No
mental state	Yes	No	No	No

As nouns, mental state is a hypernym of cognitive state; that is, mental state is a word with a broader meaning than cognitive state:

cognitive state: the state of a person's cognitive processes
mental state: (psychology) a mental condition in which the qualities of a state are relatively constant even though the state itself may be dynamic

Other hypernyms of cognitive state include mental condition, psychological condition, psychological state.

cognitive state (noun)	mental state (noun)
the state of a person's cognitive processes	(psychology) a mental condition in which the qualities of a state are relatively constant even though the state itself may be dynamic