Bipolar is a spectrum disorder, where the degree of the ‘highs’ varies (the depression is usually severe throughout). Hypomania is what differentiates Bipolar II from Bipolar I. You don’t become as clearly unwell as full mania, but the core symptoms are the same. The key difference is that in full mania people tend to totally lose the ability to think clearly and therefore start behaving in really obviously strange ways, whereas in hypomania they are able to keep things together a little bit better even though they aren’t well. To give you a pretty extreme example, there was a fellow about ten years ago who was arrested after taking his employer’s yacht and sailing it to Tasmania. When the police investigated, they found that during previous episodes he had made off with a bunch of other stuff and was storing it all in a warehouse he had rented. If I had to guess, I’d say that he had had hypomanic episodes in the beginning, and then when he finally had a manic episode he put caution to the wind and made off with the yacht.
