4 days is the minimum amount of days necessary for a hypomanic episode, or any length of days if hospitalization is required. Not needing much sleep is a hallmark symptom, but that is not needed for the episode. The necessary components are elevated or irritable mood, plus at least 3 (or at least 4 if mood is irritable) of the other symptoms. Lack of sleep is one of about 7 diagnostic criteria. It's the usual screening question, but not enough to diagnose or rule out bipolar. Having said all that a depression diagnosis is not necessarily "just depression." It's a more common illness, but can be just as severe and deadly for some people. But like others have said, diagnosis is less important than finding the right treatment.