frame of mind vs mental state

frame of mind and mental state both are nouns.

Word	Noun	Adjective	Verb	Adverb
frame of mind	Yes	No	No	No
mental state	Yes	No	No	No

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

frame of mind: a temporary psychological state
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 frame of mind include temporary state, mental condition, psychological condition, psychological state.

frame of mind (noun)	mental state (noun)
a temporary psychological state	(psychology) a mental condition in which the qualities of a state are relatively constant even though the state itself may be dynamic