Below is an old-ish BBC documentary about Manic Depression, also known as Bipolar Disorder, presented by Stephen Fry. There are two subtypes of bipolar disorder: Bipolar I and Bipolar II. According to the Diagnostic Statistical Manual of Psychiatric Disorders (DSM-VI), a person has to have an episode of mania for at least a week in his/her lifetime in order to be diagnosed with Bipolar I. A diagnosis of Bipolar II on the other hand, requires an episode of hypomania and an episode of depression.
Enjoy the documentary: