cyclothymia vs manic depression

cyclothymia and manic depression both are nouns.

Word	Noun	Adjective	Verb	Adverb
cyclothymia	Yes	No	No	No
manic depression	Yes	No	No	No

As nouns, manic depression is a hypernym of cyclothymia; that is, manic depression is a word with a broader meaning than cyclothymia:

cyclothymia: a mild bipolar disorder that persists over a long time
manic depression: a mental disorder characterized by episodes of mania and depression

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

cyclothymia (noun)	manic depression (noun)
a mild bipolar disorder that persists over a long time	a mental disorder characterized by episodes of mania and depression