manic depressive illness vs manic depression

manic depressive illness and manic depression both are nouns.

Word	Noun	Adjective	Verb	Adverb
manic depressive illness	Yes	No	No	No
manic depression	Yes	No	No	No

As nouns, manic depressive illness and manic depression are synonyms defined as:

manic depressive illness and manic depression: a mental disorder characterized by episodes of mania and depression

Other synonyms of manic depressive illness include bipolar disorder, manic-depressive psychosis.

manic depressive illness (noun)	manic depression (noun)
a mental disorder characterized by episodes of mania and depression	a mental disorder characterized by episodes of mania and depression