What is the difference detween chronic depression and unipolar depression?

Overlapping terms: "chronic depression" simply means the depression has be persistently present for a long time, typically years or longer. "unipolar depression" means that the person only has depression, as opposed to bipolar affective disorder, where both depression & mania occur. The formal terminology is major depression, with various modifiers that describe severity, duration, & persistence, etc..

Chronic depression: has to do with long duration. Where are unipolar depression has to do with episode (s) of depression which do not include episodes of mania or hypomania.