Hi, April. Quick answer: The threshold for BP I is a manic episode (which tend to be 911 situations) while for BP II the threshold is hypomania (regarded as mania lite). But don't be fooled into thinking BP II is a milder form of bipolar. For both BP I and BP II, depression is the more disabling and pervasive and life-threatening part of the illness. For those with BP II, their lives may seem to be nothing but depression, which may make them wish for mania to break things up. Those are the basics. I encourage you to do your own research.