depressed vs down in the mouth

depressed and down in the mouth both are adjectives.

Word	Noun	Adjective	Verb	Adverb
depressed	No	Yes	No	No
down in the mouth	No	Yes	No	No

As adjectives, depressed and down in the mouth are synonyms defined as:

Other synonyms of depressed include blue, dispirited, down, downcast, downhearted, gloomy, grim, low-spirited, low.

depressed (adjective)	down in the mouth (adjective)
filled with melancholy and despondency	filled with melancholy and despondency
lower than previously
flattened downward as if pressed from above or flattened along the dorsal and ventral surfaces