Answering your questions this evening is Dr. Stephen Aronson. Dr. Aronson is from the University of Michigan, where he is a clinical assistant professor. The energy increase tends to happen in manic phases. Bipolar means depressive as well as manic stages.
Unipolar depression is just the depressed phase.
They're separate entities biologically. Unipolar depression is far more common. Fortunately they're much less used today. Prozac, Paxil and Zoloft probably account for the majority of prescriptions today. The side effects can include insomnia if taken in evening rather than daytime.