mental disease vs mental state

mental disease and mental state both are nouns.

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

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

mental disease: any disease of the mind; the psychological state of someone who has emotional or behavioral problems serious enough to require psychiatric intervention
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 mental disease include mental condition, psychological condition, psychological state.

mental disease (noun)	mental state (noun)
any disease of the mind; the psychological state of someone who has emotional or behavioral problems serious enough to require psychiatric intervention	(psychology) a mental condition in which the qualities of a state are relatively constant even though the state itself may be dynamic